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AN EXAMINATION 


WEISMANNISM 


j Sag 
GEORGE JOHN “ROMANES, MASEL DD. rR.S, 


HONORARY FELLOW OF GONVILLE AND CAIUS COLLEGE, 
CAMBRIDGE 


CHICAGO 
THE OPEN COURT PUBLISHING COMPANY 
1893 


PUBLISHER'S NOTE. 


Several parts of this book, especially the article in Chapter 
Five, pp. 147-163, on ‘‘ Weismann’s Theory of Evolution (1893),” 
have been published and copyrighted in Zhe Open Court. 


CON TE Nes 


} 


CHAP. Ai el 
I. STATEMENT OF WEISMANN’S SYSTEM UP TO THE 


YEAR 1886 . , ; ; ‘ F ‘ ; 


II. LATER ADDITIONS TO WEISMANN’S SYSTEM UP TO THE 
YEAR 1892 . : : : ; ‘ ‘ ° : 


III. WEISMANN’S THEORY OF HEREDITY (1891) . ° 


IV. EXAMINATION OF WEISMANN’'S THEORY OF EVOLUTION 


(1891) . : : : ° . ° : - : 

V. WEISMANNISM UP TO DATE (1893) . ° ° ° “ 
APPENDIX I.—ON GERM-PLASM . . ° ° ° ‘ 
II—On TELEGONY . : : : : : ; 


>] 


PAGE 


28 


48 


86 


11 


173 


1g! 





uke Teka 1B 


AS already stated in the Preface to the second 
edition of Darwin and after Darwin, Part I, severe 
and protracted illness has hitherto prevented me from 
proceeding to the publication of Part II. It is now 
more than a year since I had to suspend work of 
every kind, and therefore, although at that time 
Part II was almost ready for press, I have not yet been 
able to write its concluding chapters. Shortly before 
and during this interval Professor Weismann has 
produced his essays on Amphimixis and The Germ- 
plasm. ‘These works present extensive additions to, 
and considerable modifications of, his previous theories 
as collected together in the English translation, under 
the title Assays on Heredity, Vol. 7. Consequently, 
it has become necessary for me either to re-write the 
examination of his system which I had prepared for 
Part II of my own treatise, or else to leave that 
examination as it stood, and to add a further chapter 
dealing with those later developments of his system 
to which I have just alluded. After due reflection 


A 3 


V1 Preface. 


I have decided upon the latter course, because in this 
way we are most likely to obtain a clear view of the 
growth of Weismann’s elaborate structure of theories 
—a view which it is almost necessary, for the purposes 
of criticism, that we should obtain. 

Having decided upon this point, it occurred to me 
that certain advantages would be gained by removing 
the whole criticism from the position which it was 
originally intended to occupy as a section of my 
forthcoming volume on the Post-Darwinian period. 
For, in consequence of the criticism having been 
written at successive intervals during the last six or 
eight years as Professor Weismann’s works succes- 
sively appeared, it has now swelled to a bulk which 
would unduly encumber the volume just mentioned. 
Again, the growth of Professor Weismann’s system 
has of late become so rapid, that if the criticism 
is to keep pace with it in future, the best plan 
will doubtless be the one which it is now my 
intention to adopt—viz., to publish the criticism in 
a separate form, and in comparatively small editions, 
so that further chapters may be added with as much 
celerity as Professor Weismann may hereafter pro- 
duce his successive works. Lastly, where so much 
elaborate speculation and so many changes of doctrine 
are concerned, it is inevitable that some misunder- 
standings on the part of a critic are likely to have 
arisen; and therefore, should Professor Weismann 
deem it worth his while to correct any such failings 
on my part, the plan of publication just alluded to 


Preface. vil 


will furnish me with the best opportunity of dealing 
with whatever he may have to say. 

It must be understood, however, that under the 
term “ Weismannism” I do not include any reference 
to the important question with which the name of 
Weismann has been mainly associated—i.e., the 
inheritance or non-inheritance of acquired characters. 
This is a question of fact, which stands to be an- 
swered by the inductive methods of observation and 
experiment: not by the deductive methods of general 
reasoning. Of course Professor Weismann is fully 
entitled to assume a negative answer as a basis 
whereon to construct his theory of the continuity of 
germ-plasm ; but no amount of speculation as to what 
the mechanism of heredity is likely to be if once this 
assumption is granted, can even so much as tend to 
prove that the assumption itself is true. Therefore, 
in this “examination of Weismannism” I intend to 
restrict our attention to the elaborate system of 
theories which Weismann has reared upon his funda- 
mental postulate of the non-inheritance of acquired 
characters, reserving for my next volume our con- 
sideration of this postulate itself. 

Lest, however, it should be felt that “an examina- 
tion of Weismannism” in which the question of the 
transmission of acquired characters is omitted must 
indeed prove a case of Hamlet without the Prince of 
Denmark, I may be allowed to make two observations. 
In the first place, this great question of fact is clearly 
quite distinct from that of any theories which may be 


Vill Preface. 


framed upon either side of it. And, in the second 
place, the question was not raised by Weismann. It 
appears, indeed, from what he says, that he never 
caught a glimpse of it till about ten years ago, and 
that he then did so as a result of his own independent 
thought. Moreover, it is perfectly true that to him 
belongs the great merit of having been the first to 
call general attention to the subject, and so to arouse 
a world-wide interest with reference to it. But to 
suppose that the question was first propounded by 
Weismann is merely to display a want of acquaint- 
ance with the course of Darwinian thought in this 
country. As far back as 1874 I had long conversa- 
tions with Darwin himself upon the matter, and under 
his guidance performed what I suppose are the only 
systematic experiments which have ever been under- 
taken with regard to it. These occupied more than 
five years of almost exclusive devotion; but, as 
they all proved failures, they were never published. 
Therefore I here mention them merely for the pur- 
pose of showing that the idea of what is now called 


P] 


a “continuity of germ-plasm”’ was present to Dar- 
win’s mind as a logically possible alternative to the 
one which he adopted in his theory of pangenesis—an 
alternative, therefore, which he was anxious to ex- 
clude by way of experimental disproof. If it be said 
that no one could have been aware of this in the absence 
of publication, I reply that I think it may be perceived 
by any one who reads attentively his chapter on 


Pangenesis. Moreover, early in the seventies his 


Preface. 1x 


cousin, Mr. Francis Galton, published a “ Theory of 
Heredity,’ which, as we shall see in the course of 
the following pages, presented as distinctly as could 
possibly be presented the question of the transmission 
of acquired characters, and answered it in almost 
exactly the same manner as Weismann did about ten 
years later. Lastly, as Weismann has himself been 
careful to point out, he was likewise anticipated in this 
matter by Jager (1878), and Nussbaum and Rauber 
(1880). 

For these reasons, then, I exclude this question 
from the following examination of what I think we 
ought to understand as distinctively “ Weismannism.” 


Guyer 


CHRIST CHURCH, OXFORD, 
July, 1893 


AN 
EXAMINATION OF WEISMANNISM. 


Gr As Te labo aa 


STATEMENT OF WEISMANN’S SYSTEM 
UP TO THE YEAR 18861. 


SEEING that Professor Weismann’s theory of 
heredity, besides being somewhat elaborate in itself, is 
presented in a series of disconnected essays, originally 
published at different times, it is a matter of no small 
difficulty to gather from the present collection of 
them a complete view of the system as a whole. 
Therefore I propose to give a brief sketch of his 
several cognate theories, arranged in a manner 
calculated to show their logical connexion one with 
another. And, in order also to show the relation in 
which his resulting theory of heredity stands to what 
has hitherto been the more usual way of regarding 
the facts, I will begin by furnishing a similarly con- 
densed account of Mr. Darwin’s theory upon the 
subject. It will be observed that these two theories 
constitute the logical extremes of explanatory thought; 
and therefore it may be said, in a general way, that 


1 Considerable portions of this chapter have already appeared as an 
article in the Contemporary Review for May, 1890. My thanks are due 
to the editor for kindly allowing me to reproduce them here. 


B 


2 An Examination of Wetsmannism. 


all other modern theories of heredity—such as those of 
Spencer, Hackel, Elsberg, Galton, Nageli, His, Brooks, 
Hertwig, and De Vries—occupy positions more or less 
intermediate between these two extremes. Therefore, 
also, we need not wait to consider these intermediate 
theories |. 

When closely analyzed, Mr. Darwin’s theory—or 
the “provisional hypothesis of Pangenesis ”—will 
be found to embody altogether seven assumptions, 
namely :— 

1. That all the component cells of a multicellular 
organism throw off inconceivably minute germs, or 
“eemmules,” which are then dispersed throughout the 
whole system. 

2. That these gemmules, when so dispersed and 
supplied with proper nutriment, multiply by self- 
division, and, under suitable conditions, are capable of 
developing into physiological cells like those from 
which they were originally and severally derived. 

3. That, while still in this gemmular condition, 
these cell-seeds have for one another a mutual affinity, 
which leads to their being collected from all parts of 
the system by the reproductive glands of the organ- 
ism; and that, when so collected, they go to con- 
stitute the essential material of the sexual elements— 


* In as far as these sundry theories of heredity are not more or less 
intermediate between those of | arwin and Weismann, the differences 
have reference either to points of comparative detail, or else to the 
introduction of ideas derived from chemistry and physics—whereby it 
is sought to show that the principles of chemical combination and of 
thythmic vibration may have a more or less considerable share in the 
matter. For my own part I do not see that the introduction of such 
ideas has been of any avail in helping—even hypothetically—to explain 
the phenomena of heredity; and therefore I do not deem it worth our 
while to consider them. 


Statement of Wersmann's System (1886). 3 


ova and spermatozoa being thus aggregated packets 
of gemmules, which have emanated from all the cells 
of all the tissues of the organism. 

4. That the development of a new organism, out of 
the fusion of two such packets of gemmules, is due to 
a summation of all the developments of some of the 
gemmules which these two packets contain. 

5. That a large proportional number of the gem- 
mules in each packet, however, fail to develop, and 
are then transmitted in a dormant state to future 
generations, in any of which they may be developed 
subsequently—thus giving rise to the phenomena of 
reversion or atavism. 

6. That in all cases the development of gemmules 
into the form of their parent cells depends on their 
suitable union with other partially developed gem- 
mules, which precede them in the regular course of 
growth. 

7. That gemmules are thrown off by all physio- 
logical cells, not only during the adult state of the 
organism, but during all stages of its development. 
Or, in other words, that the production of these cell- 
seeds depends upon the adult condition of parent cells: 
not upon that of the multicellular organism as a 
whole. 

At first sight it may well appear that we have 
here a very formidable array of assumptions. But 
Darwin ably argues in favour of each of them by 
pointing to well-known analogies, drawn from the 
vital processes of living cells both in the protozoa 
and metazoa. For example, it is already a_ well- 
recognized doctrine of physiology that each cell of 
a metazoon, or multicellular organism, though to 

B 2 


4. An Examination of Wetsmannism. 


a large extent dependent on others, is likewise to 
a certain extent independent or autonomous, and has 
the power of multiplying by self-division. Therefore, 
as it is certain that the sexual elements (and also buds 
of all descriptions) include formative material of some 
kind, the first assumption — or that which supposes such 
formative matter to be particulate—is certainly not 
a gratuitous assumption. 

Again, the second assumption—viz., that this par- 
ticulate and formative material is dispersed throughout 
all the tissues of the organism—is sustained by the fact 
that, both in certain plants and in certain invertebrated 
animals, a severed portion of the organism will develop 
into an entire organism similar to that from which it 
was derived, as, for example, is the case with a leaf of 
Begonia, and with portions cut from certain inver- 
tebrated animals, such as sea-anemones, jelly-fish, &c. 
This well-known fact in itself seems enough to prove 
that the formative material in question must certainly 
admit, at all events in many cases, of being distributed 
throughout all the tissues of living organisms. 

The third assumption—or that which supposes 
the formative material to be especially aggregated in 
the sexual elements—is not so much an assumption 
as a statement of obvious fact ; while the fourth, fifth, 
sixth, and seventh assumptions all follow deductively 
from their predecessors. In other words, if the first 
and second assumptions be granted, and if the theory 
is to comprise all the facts of heredity, then the 
remaining five assumptions are bound to follow. 

To the probable objection that the supposed gem- 
mules must be of a size impossibly minute—seeing 
that thousands of millions of them would have to 


Statement of Wetsmann's System (1886). 5 


be packed into a single ovum or spermatozoon— 
Darwin opposes a calculation that a cube of glass or 
water, having only one ten-thousandth of an inch to 
a side, contains somewhere between sixteen and a 
hundred and thirty-one billions of molecules. Again, 
as touching the supposed power of multiplication on 
the part of his gemmules, he alludes to the fact 
that infectious material of all kinds exhibits a ratio 
of increase quite as great as any that his theory 
requires to attribute to gemmules. Furthermore, with 
respect to the elective affinity of gemmules, he 
remarks that “in all ordinary cases of sexual repro- 
duction, the male and female elements certainly have 
an elective affinity for each other”: of the ten 
thousand species of Compositae, for example, “ there 
can be no doubt that if the pollen of all these 
species could be simultaneously placed on the stigma 
of any one species, this one would elect, with unerring 
certainty, its own pollen.” 

Such, in brief outline, is Mr. Darwin’s theory of 
Pangenesis. 

Professor Weismann’s theory of Germ-plasm is 
fundamentally based upon the great distinction, 
in respect of their transmissibility, between char- 
acters that are congenital and characters that are 
acquired. By a congenital character is meant any 
individual peculiarity, whether structural or mental, 
with which the individual is born. By an acquired 
character is meant any peculiarity which the individual 
may subsequently develop in consequence of its own 
individual experience. For example, a man may be 
born with some malformation of one of his fingers ; or 
he may subsequently acquire such a malformation as 


6 An Examination of Weismannism. 


the result of accident or disease. Now, in the former 
case—i.e., in that where the malformation is con- 
genital—it is extremely probable that the peculiarity 
will be transmitted to his children; while in the latter 
case—i.e., where the malformation is subsequently 
acquired—it is virtually certain that it will not be 
transmitted to his children. And this great difference 
between the transmissibility of characters that are 
congenital and characters that are acquired extends 
universally as a general law throughout the vegetable 
as well as the animal kingdom, and in the province of 
mental as in that of bodily organization. Of course 
this general law has always been well known, and 
more or less fully recognized by all modern physi- 
ologists and medical men. But before the subject 
was taken up by Professor Weismann, it was generally 
supposed that the difference in question was one of 
degree, not one of kind. In other words, it was 
assumed that acquired characters, although not so 
fully—and therefore not so certainly—inherited as 
congenital characters, nevertheless were inherited in 
some lesser degree; so that if the same character 
continued to be developed successively in a number 
of sequent generations, what was at first only a slight 
tendency to be inherited would become by summation 
a more and more pronounced tendency, till eventually 
the acquired character might be as strongly inherited 
as any other character which was ad znztio congenital. 
Now it is the validity of this assumption that is 
challenged by Professor Weismann. He says there is 
no evidence of any acquired characters being in any 
degree inherited ; and, therefore, that in this important 
respect they may be held to differ from congenital 


Statement of Wersmann's System (1886). 7 


characters in kind. On the supposition that they do 
thus differ in kind, he furnishes a very attractive 
theory of heredity, which serves at once to explain 
the difference, and to represent it as a matter of 
physiological impossibility that any acquired char- 
acter can, under any circumstances whatsoever, be 
transmitted to progeny. 

But, in order fully to comprehend this theory, it is 
desirable first of all to explain Professor Weismann’s 
views upon certain other topics which are intimately 
connected with—and, indeed, logically sequent upon— 
the use to which he puts the distinction just men- 
tioned. 

Starting from the fact that unicellular organisms 
multiply by fission and gemmation, he argues that, 
aboriginally and potentially, life is immortal. For 
when a protozoon divides itself into two more or less 
equal parts by fission, and each of the two halves 
thereupon grows into another protozoon, it does not 
appear that there has been any death on the part of 
the living material involved; and inasmuch as this 
process of fission goes on continuously from generation 
to generation, there is seemingly never any death 
on the part of such protoplasmic material, although 
there is a continuous addition to it as the numbers 
of individuals increase. Similarly, in the case of 
gemmation, when a protozoon parts with a small 
portion of its living material in the form of a bud, 
this portion does not die, but develops into a new 
individual; and, therefore, the process is exactly 
analogous to that of fission, save that a small 
instead of a large part of the parent substance is 
involved. Now, if life be thus immortal in the 


8 An Examination of Wetsmannism. 


case of unicellular organisms, why should it have 
ceased to be so in the case of multicellular? Weis- 
mann’s answer is, that all the multicellular organisms 
propagate themselves, not exclusively by fission or 
gemmation, but by sexual fertilization, where the 
condition to a new organism arising is that minute 
and specialized portions of two parent organisms 
should fuse together. Now, it is evident that with 
this change in the method of propagation, serious 
disadvantage would accrue to any species if its sexual 
individuals were to continue to be immortal; for in 
that case every species which multiplies by sexual 
methods would in time become composed of indi- 
viduals broken down and decrepit through the results 
of accident and disease—always operating and ever 
accumulating throughout the course of their immortal 
lives. Consequently, as soon as sexual methods of 
propagation superseded the more primitive a-sexual 
methods, it became desirable in the interests of the 
sexually-propagating species that their constituent 
individuals should cease to be immortal, so that the 
species should always be recuperated by fresh, young, 
and well-formed representatives. Consequently, also, 
natural selection would speedily see to it that all 
sexually-propagating species should become deprived 
of the aboriginal endowment of immorality, with the 
result that death is now universal among all the 
individuals of such species—that is to say, among 
all the metazoa and metaphyta. Nevertheless, it is 
to be remembered that this destiny extends only to 
the parts of the individual other than the contents 
of those specialized cells which constitute the repro- 
ductive elements. For although in each individual 


Statement of Wersmann’s System (1886). 9 


metazoon or metaphyton an innumerable number of 
these specializec cells are destined to perish during 
the life, or with the death, of the organism to which 
they belong, this is only due to the accident, so to 
speak, of their contents not having met with their 
complements in the opposite sex: it does not belong 
to their essential nature that they should perish, seeing 
that those which do happen to meet with their com- 
plements in the opposite sex help to form a new living 
individual, and so on through successive generations 
ad infinitum. Therefore the reproductive elements 
of the metazoa and metaphyta are in this respect 
precisely analogous to the protozoa: potentially, or in 
their own nature, they are immortal; and, like the 
protozoa, if they die, their death is an accident due to 
unfavourable circumstances. But the case is quite 
different with all the other parts of a multicellular 
organism. Here, no matter how favourable the cir- 
cumstances may be, every cell contains within itself, 
or in its very nature, the eventual doom of death. 
Thus, of the metazoa and metaphyta it is the 
“oerm-plasms” alone that retain their primitive 
endowment of everlasting life, passed on continuously 
through generation after generation of successively 
perishing organisms. 

So far, it is contended, we are dealing with matters 
of fact. It must be taken as true that the protoplasm 
of the unicellular organisms, and the germ-plasm of the 
multicellular organisms, has been continuous through 
the time since life first appeared upon this earth; and 
although large quantities of each are perpetually dying 
through being exposed to conditions unfavourable to 
life, this, as Weismann presents the matter, is quite 


10 An Examination of Wetsmannism. 


a different case from that of all the other constituent 
parts of multicellular organisms, which contain within 
themselves the doom of death. Furthermore, it appears 
extremely probable that this doom of death has been 
brought about by natural selection for the reasons 
assigned by Weismann—namely, because it is for the 
benefit of all species which perpetuate themselves by 
sexual methods, that their constituent individuals 
should not live longer than is necessary for the sake 
of orginating the next generation, and fairly starting 
it in its own struggle for existence. For Weismann 
has shown, by a somewhat laborious though still 
largely imperfect research, that there is throughout 
all the metazoa a general correlation between the 
natural lifetime of individuals composing any given 
species and the age at which they reach maturity, 
or first become capable of procreation. This general 
correlation, however, is somewhat modified by the 
time during which progeny are dependent upon their 
parents for support and protection. Nevertheless, 
it is evident that this fact tends rather to confirm 
the view that expectation of life on the part of 
individuals has in all cases been determined with 
strict reference to the requirements of propagation, 
if under propagation we include the rearing as well 
as the production of offspring. I may observe in 
passing that I do not think this general law can 
be found to apply to plants in nearly so close 
a manner as Weismann has shown it to apply to 
animals; but, leaving this consideration aside, I think 
that Weismann has made out a good case in favour 
of such a general law with regard to animals}. 


1 See Appendix. 


Statement of Wersmann's System (1886). 11 


We have come, then, to these results. Proto- 
plasm was originally immortal, barring accidents; 
and it still continues to be immortal in the case of 
unicellular organisms which propagate a-sexually. 
But in the case of all multicellular organisms, which 
propagate sexually, natural selection has_ reduced 
the term of life within the smallest limits that in 
each given case are compatible with the performance 
of the sexual act and the subsequent rearing of pro- 
geny—reserving, however, the original endowment 
of immortality for the germinal elements, whereby 
a continuum of life has been secured from the earliest 
appearance of life until the present day. 

Now, in view of these results the question arises,— 
Why should the sexual methods of propagation have 
become so general, if their effect has been that of 
determining the necessary death of all individuals 
presenting them? Why, in the course of organic 
evolution, should these newer methods have been 
imposed on all the higher organisms, when the conse- 
quence is that all these higher organisms must pay 
for the innovation with their lives? Weismann’s 
answer to this question is as interesting and ingenious 
as all that has gone before. Seeing that sexual pro- 
pagation is so general as to be practically universal 
among multicellular organisms, it is obvious that in 
some way or another it must have had a most important 
part to play in the general scheme of organic evolution. 
What, then, is the part that it does play? What is 
its raison @étre? Briefly, according to Weismann, its 
function is that of furnishing congenital variations to 
the ever-watchful agency of natural selection, in order 
that natural selection may always preserve the most 


12 An Examination of Wetsmannism. 


favourable, and pass them on to the next generation 
by heredity. That sexual propagation is well calcu- 
lated to furnish congenital variations may easily be 
rendered apparent. We have only to remember that 
at each union there is a mixture of two sets of 
germinal elements; that each of these was in turn 
the product of two other sets in the preceding 
generation, and so backwards ad infinitum in an 
ever doubling ratio. Remembering this, it follows 
that the germinal elements of no one member of 
a species can ever be the same as those of any other 
member born of different parents; on the contrary, 
while both are enormously complex products, each 
has had a different ancestral history, such that 
while one presents the congenital admixtures of 
thousands of individuals in one line of descent, the 
other presents similar admixtures of thousands of 
other individuals in a different line of descent. Con- 
sequently, when in any sexual union two of these 
enormously complex germinal elements fuse together, 
and constitute a new individual out of their joint 
endowments, it is perfectly certain that that individual 
cannot be exactly like any other individual of the 
same species which has been born of different parents. 
The chances must be infinity to one against any single 
mass of germ-plasm being exactly like any other mass 
of germ-plasm ; while any amount of latitude as to 
difference is allowed, up to the point at which the 
difference becomes too pronounced to satisfy the 
conditions of fertilization—in which case, of course, 
no new individual is born. Hence, theoretically, we 
have here a sufficient cause for all individual variations 
of a congenital kind that can possibly occur within 


Statement of Wetsmann's System (1886). 13 


the limits of fertility, and, therefore, that can ever 
become actual in living organisms. In point of fact, 
Weismann believes—or, at any rate, provisionally 
maintains—that this is the sole and only cause of 
variations that are congenital, and therefore (according 
to his views) transmissible by heredity. Now, whether 
or not he is right as regards these latter points, I 
think there can be no question that sexual propagation 
is, at all events, one of the main causes of congenital 
variation ; and seeing of what enormous importance 
congenital variation must always have been in 
supplying material for the operation of natural se- 
lection, we appear to have found a most satisfactory 
answer to our question,— Why has sexual propagation 
become so universal among all the higher plants and 
animals? It has become so because it is thus shown 
to have been the condition to producing congenital 
variations, which in turn constitute one of the primary 
conditions to the working of natural selection. 
Having got thus far, I should like to make two or 
three subsidiary remarks, In the first place, it ought 
to be observed that this theory touching the causes of 
congenital variations was not originally propounded 
by Professor Weismann, but occurs in the writings of 
several previous authors, and is expressly alluded to 
by Darwin!. Nevertheless, it occupies so prominent 
a place in Weismann’s system of theories, and has by 
him been wrought up so much more elaborately than 
by any of his predecessors, that we are entitled to 
regard it as, par excellence, the Weismannian theory of 
variation. In the next place, it ought to be observed 
that Weismann is careful to guard against the 


1 E.g., Variation, &c., vol. i. pp. 197, 398; vol. ii. pp. 237, 252. 


14 An Examination of Wetsmannism. 


seductive fallacy of attributing the origin of sexual 
propagation to the agency of natural selection. Great 
as the benefit of this newer mode of propagation must 
have been to the species presenting it, the benefit 
cannot have been conferred by. natural selection, 
secing that the benefit arose from the fact of the 
new method furnishing material to the operation 
of naturai selection, and therefore constituting the 
condition to the agency of natural selection having 
been ‘called ‘intowexistence’ at alla” (Of inesother 
words, we cannot attribute to natural selection 
the origin of sexual reproduction without involv- 
ing ourselves in the absurdity of supposing natural 
selection to have originated the conditions of its 
own activity’. What the causes may have been 


1 Since this chapter was written and sent as a contribution to the 
Contemporary Keview, Professor Weismann has published in Vature 
(Feb. 6, 1890) an elaborate answer to a criticism of his theory by 
Professor Vines (Oct. 24, 1889). In the course of this answer Professor 
Weismann says that he does attribute the origin of sexual reproduction 
to natural selection. This directly contradicts what he says in his 
“ssays ; and, for the reasons given in the text, appears to me an illogical 
departure from his previously logical attitude. I herewith append 
quotations, in order to reveal the contradiction. 

“But when I maintain that the meaning of sexual reproduction is to 
render possible the transformation of the higher organisms by means of 
natural selection, such a statement is not equivalent to the assertion that 
sexual reproduction originally came into existence in order to achieve 
this end. The effects which are now produced by sexual reproduction 
did not constitute the causes which led to its first appearance. Sexual 
reproduction came into existence before it could lead to hereditary 
individual variability [i.e., to the possibility of natural selection]. Its 
first appearance must, therefore, have had some other cause [than 
natural selection}; but the nature of this cause can hardly be determined 
with any degree of certainty or precision from the facts with which we 
are at present acquainted.”—Fssay on the Significance of Sexual Re- 
production in the Theory of Natural Selection. English Translation, 
pp. 281-282. 

“Tam still of opinion that the origin of sexual reproduction depends 


Statement of Wersmann's System (1886). 15 


which originally led to sexual reproduction is at 
present a matter -jhat awaits suggestion by way of 
hypothesis ; and, therefore, it now only remains to add 
that the general structure of Professor Weismann’s 
system of hypotheses leads to this curious result — 
namely, that the otherwise ubiquitous and (as he 
supposes) exclusive dominion of natural selection 
stops short at the protozoa, over which it cannot 
exercise any influence at all. For if natural selection 
depends for its activity on the occurrence of congenital 
variations, and if congenital variations depend for 
their occurrence on sexual modes of reproduction, it 
follows that no organisms which propagate by any 
other modes can present congenital variations, or thus 
become subject to the sway of natural selection. 
And inasmuch as Weismann believes that such is the 
case with all the protozoa, as well as with all 
parthenogenetic organisms he does not hesitate to 
accept the necessary conclusion that in these cases 
natural selection is without any jurisdiction. How, 
then, does he account for individual variations in 
the protozoa? And, still more, how does he ac- 
count for the origin of their innumerable species? 
He accounts for both these things by the direct 
action of external conditions of life. In other words, 
so far as the unicellular organisms are concerned, 
Weismann is rigidly and unconditionally an advocate 


on the advantage which it affords to the operation of natural selection. 
.. . . Sexual reproduction has arisen by and for natural selection as the 
sole means by which individual variations can be united and combined 
in every possible proportion.” —/Vature, vol. xli. p. 322. 

How such contradictory statements can be reconciled I do not 
perceive; but they furnish a good example of the extreme laxity with 
which the term “ natural selection” is used by ultra-Darwinians, 


16 Ax Examination of Wetsmannisme. 


of the theory of Lamarck—just as much as in the case 
of all the multicellular organisms Jxe is rigidly and un- 
conditionally an opponent of that theory. Nevertheless, 
there is here no inconsistency: on the contrary, it is 
consistency with the logical requirements of his theory 
that leads to this sharp partitioning of the unicellular 
from the multicellular organisms with respect to the 
causes of their evolution. For, according to his view, 
the conditions of propagation among the unicellular 
- organisms are such that parent and offspring are one 
and the same thing; “the child is a part, and usually 
a half, of its parent.” Therefore, if the parent has 
been in any way modified by the action of external 
conditions, it is inevitable that the child should, from 
the moment of its birth (i.e., fissiparous separation), 
be similarly modified ; and if the modifying influences 
continue in the same lines for a sufficient length of 
time, the resulting change of type may become 
sufficiently pronounced to constitute a new species, 
genus, &c. But in the case of the multicellular or 
sexual organisms, the child is not thus merely a 
severed moiety of its parent; it is the result of the 
fusion of two highly specialized and extremely minute 
particles of each of two parents. Therefore, whatever 
may be thought touching the validity of Weismann’s 
deduction that inno case can any modification induced 
by external conditions on these parents be trans- 
mitted to their progeny, at least we must recognize 
the validity of the distinction which he draws between 
the facility with which such transmission must take 
place in the unicellular organisms, as compared with 
the difficulty—or, as he believes, the impossibility— 
of its doing so in the multicellular. 


Statement of Wetsmann’s System (1886). 17 


We are now in a position fully to understand Pro- 
fessor Weismann’s theory of heredity in all its bearings. 
Briefly stated, it is as follows. The whole organiza- 
tion of any multicellular organism is composed 
of two entirely different kinds of cells—namely, the 
germ-cells, or those which have to do with repro- 
duction, and the somatic-cells, or those which go to 
constitute all the other parts of the organism. Now, 
the somatic-cells, in their aggregations as tissues and 
organs, may be modified in numberless ways by the 
direct action of the environment, as well as by special 
habits formed during the individual lifetime of the 
organism. But although the modifications thus in- 
duced may be, and generally are, adaptive—such as 
the increased muscularity caused by the use of muscles, 
“ practice making perfect ” where neural adjustments 
are concerned, and so on,—in no case can these so- 
called acquired, or “ somatogenetic,” characters exer- 
cise any influence upon the germ-cells, such that 
they should reappear in the next generation as con- 
genital, or “ blastogenetic,” characters. For, according 
to the theory, the germ-cells as to their germinal 
contents differ in kind from the. somatic-cells, and 
have no other connexion or dependence upon them 
than that of deriving from them their food and 
lodging. So much for the somatic-cells. 

Turning now to the germ-cells, these are the re- 
ceptacles of what Weismann calls the germ-plasm ; 
and this it is that he supposes to differ in kind 
from all the other constituent elements of the 
organism. For the germ-plasm he believes to have 
had its origin in the unicellular organisms, and to 
have been handed down from them in one continuous 

C 


18 An Examination of Wetsmannism. 


stream through all successive generations of multi- 
cellular organisms. Thus, for example, suppose that 
we take a certain guantum of germ-plasm as this 
occurs in any individual organism of to-day. A 
minute portion of this germ-plasm, when mixed 
with a similarly minute portion from another in- 
dividual, goes to form a new individual. But, in 
doing so, only a portion of this minute portion is 
consumed ; the residue is stored up in the germinal 
cells of the new individual, in order to secure that 
continuity of the germ-plasm which Weismann 
assumes as the necessary basis of his whole theory. 
Furthermore, he assumes that this overplus portion of 
germ-plasm, which is so handed over to the custody 
of the new individual, is there capable of growth or 
multiplication at the expense of the nutrient materials 
which are supplied to it by the new soma in which 
it finds itself located; while in thus growing, or 
multiplying, it faithfully retains its highly complex 
structure, so that in no one minute particular does 
any part of a many thousand-fold increase differ, as 
to its ancestral characters, from that inconceivably 
small overplus which was first of all entrusted to the 
embryo by its parents. Therefore one might re- 
present the germ-plasm by the metaphor of a yeast- 
plant, a single particle of which may be put into a vat 
of nutrient fluid: there it lives and grows upon the 
nutriment supplied, so that a new particle may next 
be taken to impregnate another vat, and so on ad 
mfinttum. Here the successive vats would represent 
successive generations of progeny; but, to make the 
metaphor complete, one would have to suppose that 
in each case the yeast-cell was required to begin by 


Statement of Wetsmann's System (1886). 19 


making its own vat of nutrient material, and that it 
was only the residual portion of the cell which was 
afterwards able to grow and multiply. But although 
the metaphor is thus necessarily a clumsy one, it 
may serve to emphasize the all-important feature of 
Weismann’s theory—namely, the almost absolute 
independence of the germ-plasm. For, just as the 
properties of the yeast-plant would be in no way 
affected by anything that might happen to the vat, 
short of its being broken up or having its malt 
impaired, so, according to Weismann, the properties 
of the germ-plasm cannot be affected by anything 
that may happen to its containing soma, short of the 
soma being destroyed or having its nutritive functions 
disordered. 

Such being the re'ations that are supposed to 
obtain between the soma and its germ-plasm, we have 
next to observe what is supposed to happen when, 
in the course of evolution, some modification of the 
ancestral form of the soma is required in order to 
adapt it to some change on the part of its environ- 
ment. In other words, we have to consider Weis- 
mann’s views on the modus operandi of adaptive 
development, with its result in the origination of new 
species. 

Seeing that, according to the theory, it is only con- 
genital variations which can be inherited, all variations 
subsequently acquired by the intercourse of individuals 
with their environment, however beneficial such 
variations may be to these individuals, are ruled out 
as regards the species. Not falling within the 
province of heredity, they are blocked off in the first 
generation, and therefore present no significance at 

C 2 


20 An Examination of Weismannism. 


all in the process of organic evolution. No matter 
how many generations of eagles. for instance. may have 
used their wings for purposes of flight ; and no matter 
how great an increase of muscularity, of endurance, and 
of skill, may thus have been secured to each genera- 
tion of eagles as the result of individual exercise ; 
all these advantages are entirely lost to progeny, and 
young eagles have ever to begin their lives with no 
more benefit bequeathed by the activity of their 
ancestors than if those ancestors had all been barn- 
door fowls. The only material which is of any count 
as regards the species, or with reference to the process 
of evolution, are fortuitous variations of the congenital - 
kind. Among all the numberless congenital varia- 
tions, within narrow limits, which are perpetually 
occurring in each generation of eagles, some will have 
reference to the wings; and although these will be 
fortuitous, or occurring indiscriminately in all direc- 
tions, a few of them will now and then be in the 
direction of increased muscularity, others in the 
direction of increased endurance, others in the direc- 
tion of increased skill, and so on. Now each of these 
fortuitous variations, which happens also to be a 
beneficial variation, will be favoured by natural 
selection; and, because it likewise happens to be a 
congenital variation, will be perpetuated by heredity. 
In the course of time, other congenital variations will 
happen to arise in the same directions; these will be 
added by natural selection to the advantage already 
gained, and so on, till, after hundreds and thousands of 
generations, the wings of eagles have become evolved 
into the marvellous structures which they now present. 

Such being the theory of natural selection when 


Statement of Wersmann’s System (1886). 21 


stripped of all remnants of so-called Lamarckian 
principles, we have next to consider what the theory 
means in its relation to germ-plasm. For, as before 
explained, congenital variations are supposed by 
Weismann to be due to new combinations taking 
place in the germ-plasm as a result of the union in 
every act of fertilisation of two complex hereditary 
histories. Well, if congenital variations are thus 
nothing more than variations of germ-plasm “ writ 
large” in the organism which is developed out of the 
plasm, it follows that natural selection is really 
at work upon these variations of the plasm. For, 
although it is proximately at work on the congenital 
variations of organisms after birth, it is ultimately, 
and through them, at work upon the variations of 
germ-plasm out of which the organisms arise. In 
other words, natural selection, in picking out of each 
generation those individual organisms which are by 
their congenital characters best suited to their sur- 
rounding conditions of life, is thereby picking out 
those peculiar combinations or variations of germ- 
plasm, which, when expanded into a resulting organism, 
give that organism the best chance in its struggle for 
existence. And, inasmuch as a certain overplus of 
this peculiar combination of germ-plasm is entrusted to 
that organism for bequeathing to the next generation, 
this to the next, and so on, it follows that natural 
selection is all the while conserving that originally 
peculiar combination of germ-plasm, until it happens 
to meet with some other mass of germ-plasm by mixing 
with which it may still further improve upon its original 
peculiarity, when, other things equal, natural selection 
will seize upon this improvement to perpetuate, 


22 An Examination of Wersmannism. 


as in the previous case. So that, on the whole, we may 
say that natural selection is ever waiting and watch- 
ing for such combinations of germ-plasm as will give 
the resulting organisms the best possible chance in 
their struggle for existence; while, at the same time, 
it is remorselessly destroying all those combinations 
of germ-plasm which are handed over to the custody of 
organisms not so well fitted to their conditions of life. 
It only remains to add that, according to Weis- 
mann’s theory in its strictly logical form, combinations 
of germ-plasm when once effected are so stable that 
they would never alter except as a result of entering 
into new combinations. In other words, no external 
influences or internal processes can ever change 
the hereditary nature of any particular mixture of 
gcerm-plasm, save and except its admixture with 
some other germ-plasm, which, being of a nature 
equally stable, goes to unite with the first in equal 
proportions as regards hereditary character. So that 
really it would be more correct to say that any given 
mass of germ-plasm does not change even when it 
is mixed with some other mass—any more, for in- 
stance, than a handful of sand can be said to change 
when it is mixed with a handful of clay. 
Consequently, we arrive at this curious result. 
No matter how many generations of organisms there 
may have been, and therefore no matter how many 
combinations of germ-plasm may have taken place 
to give rise to an existing population, each existing 
unit of germ-plasm must have remained of the same 
essential nature or constitution as when it was first 
started in its immortal career millions of years ago. 
Or, reverting to our illustration of sand and clay, the 


Statement of Wersmann's System (1886). 23 


particles of each must always remain the same, no 
matter how many admixtures they may undergo 
with particles of other materials, such as chalk, slate, 
&c. Now, inasmuch as it is an essential—because 
a logically necessary—part of Weismann’s theory 
to assume such absolute stability or unchangeable- 
ness on the part of germ-plasm, the question arises, 
and has to be met, What was the origin of those 
differences of character in the different germ-plasms 
of multicellular organisms which first gave rise, and 
still continue to give rise, to congenital variations 
by their mixture one with another? This important 
question Weismann answers by supposing that these 
differences originally arose out of the differences 
in the unicellular organisms, which were the ancestors 
of the primitive multicellular organisms. Now, as 
before stated, different forms of unicellular organisms 
are supposed to have originated as so many results of 
differences in the direct action of the environment. 
Consequently, according to the theory, all congenital 
variations which now occur in multicellular organisms, 
are really the distant results of variations that were 
aboriginally induced in their unicellular ancestors by 
the direct action of surrounding conditions of life. 

I think it will be well to conclude by briefly sum- 
marising the main features of this elaborate theory. 

Living material is essentially, or of its own nature, 
imperishable; and it still continues to be so in the 
case of unicellular organisms which propagate by 
fission or gemmation. But as soon as these primitive 
methods of propagation became, from whatever 
cause, superseded by sexual, it ceased to be for the 
benefit of species that their constituent individuals 


24 An Examination of Wetsmannism. 


should be immortal ; seeing that, if they continued 
to be so, all species of sexually-reproducing organisms 
would sooner or later have come to be composed of 
broken-down and decrepit individuals. Consequently, 
in all sexually-reproducing or multicellular organisms, 
natural selection set to work to reduce the term of 
individual lifetimes within the narrowest limits that 
in the case of each species were compatible with the 
procreation and the rearing of progeny. Nevertheless, 
in all these sexually-reproducing organisms the 
primitive endowment of immortality has been re- 
tained with respect to their germ-plasm, which has 
thus been continuous, through numberless genera- 
tions of perishing organisms, from the first origin of 
sexual reproduction till the present time. Now, it 
is the union of germ-plasms which is required to 
reproduce new individuals of multicellular organisms 
that determines congenital variations on the part of 
such organisms, and thus furnishes natural selection 
with the material for its work in the way of organic 
evolution—work, therefore, which is impossible in 
the case of unicellular organisms, where variation 
can never be congenital, but always determined by 
the direct action of surrounding conditions of life. 
Again, as the germ-plasm of multicellular organisms 
is continuous from generation to generation, and at 
each impregnation gives rise to a more or less novel 
set of congenital characters, natural selection, in 
picking out of each generation the congenital char- 
acters which are of most service to the organisms 
presenting them, is really or fundamentally at work 
upon those variations of the germ-plasm which in 
turn give origin to these variations of organisms 


Statement of Weismann's System (1886). 25 


that we recognize as congenital. Therefore, natural 
selection has always to wait and to watch for such 
variations of germ-plasm as will eventually prove 
beneficial to the individuals developed therefrom, 
who will then transmit this peculiar quality of germ- 
plasm to their progeny, and so on. Therefore also— 
and this is most important to remember—natural 
selection as thus working becomes the one and only 
cause of organic evolution in all the multicellular 
organisms, just as the direct action of the environ- 
ment is the one and only cause of it in the case 
of all the unicellular organisms. But inasmuch as the 
multicellular organisms were all in the first instance 
derived from the unicellular, and inasmuch as their 
germ-plasm is of so stable a nature that it can 
never be altered by any agencies internal or external 
to the organisms presenting it, it follows that all 
congenital variations are the remote consequences 
of aboriginal differences on the part of unicellular 
ancestors. And, lastly, it follows also that these 
congenital variations—although now so entirely in- 
dependent of external conditions of life, and even of 
activities internal to organisms themselves—were 
originally and exclusively due to the direct action 
of such conditions on the lives of their unicellular 
ancestors; while even at the present day no one con- 
genital variation can arise which is not ultimately 
due to differences impressed upon the protoplasmic 
substance of the germinal elements, when the parts 
of which these are now composed constituted integral 
parts of the protozoa, which were directly and differ- 
entially affected by their converse with their several 
environments. 


26 An Examination of Wetsmannism. 


Again, if for the sake of distinctness we neglect 
all these far-reaching deductions from his theory of 
heredity wnereby Weismann constructs this elaborate 
theory of organic evolution, and fasten our attention 
only upon the former, we may briefly summarize the 
fundamental difference between his theory of heredity 
and Darwin’s theory of Aeredity thus. 

Darwin’s theory of heredity is the theory of Pan- 
genesis: it supposes that al/ parts of the organism 
generate. anew in every individual the formative 
material which, when collected together in the germ- 
cells, constitutes the potentiality of a new organism; 
and that this new organism, when developed, resembles 
its parents simply because a// the formative material 
in each of the parents has been thus generated by, and 
collected from, a// parts of their respective bodies. 
Weismann’s theory of heredity, on the other hand, is 
the theory of the Coztinuzty of Germ-plasm: it supposes 
that 2o part of the parent organism generates any of 
the formative material which is to constitute the new 
organism; but that, on the contrary, this material 
stands to all the rest of the body in much the same 
relation as a parasite to its host, showing a life inde- 
pendent of the body, save in so far as the body supplies 
to it appropriate lodgement and nutrition; that in 
each generation a small portion of this substance is 
told off to develop a new body to lodge and nourish 
the ever-growing and never-dying germ-plasm—this 
new body, therefore, resembling its so-called parent 
body simply because it has been developed from one 
and the same mass of formative material ; and, lastly, 
that this formative material, or germ-plasm, has been 
continuous through all generations of successively 


Statement of Wersmann’s System (1886). 27 


perishing bodies, which therefore stand to it in much 
the same relation as annual shoots to a perennial 
stem: the shoots resemble one another simply 
because they are all grown from one and the same 
stock. 


GEA Palas ale 


LATER ADDITIONS TO WEISMANN’S SYSTEM 
UP TO THE YEAR 1892. 


I HAVE now furnished as complete a résamé as 
seems desirable for present purposes of Weismann’s 
theory of germ-plasm, considered both as a theory 
of heredity and as a sequent theory of organic 
evolution. But before proceeding to examine this 
elaborate system as a whole, I must devote another 
chapter to a further’ “statement ofp certainmmarer 
additions to—and also emendations of—the system 
as it was originally propounded. These additions 
and alterations have reference only to the theory of 
heredity: they do not affect the theory of organic 
evolution as originally deduced therefrom. More- 
over they have all been due to our more recently 
acquired knowledge touching the morphology and 
physiology of cell-nuclei: it is for the purpose of 
bringing his theory of germ-plasm into accord with 
these results of later researches that Weismann has 
thus modified the theory as it originally stood. For 
my own part, Ido not see that very much is gained 
by these newer additions and modifications ; but, be 
this as it may, they are certainly very complicated, 
and on this account I have thought it best to devote a 
separate chapter to their consideration. Furthermore, 


Later Additions up to the year 1892. 29 


not only in the opinion of Weismann himself, but also 
in that both of his friends and foes, the main question 
with which his later essays are concerned—viz., as to 
whether the nucleus of a cell is the only part of a cell 
which is concerned in the phenomena of heredity—is 
regarded as of fundamental importance to his entire 
edifice. Hence, although I cannot myself perceive 
that the indisputable importance of this question to 
any speculations on the subject of heredity is of such 
special or vital significance to Weismann’s theory, it 
becomes necessary for me to supply this further 
chapter for the purpose of presenting the further 
developments of his theory. 

First of all, Weismann has of late years considerably 
modified his original view touching the relation of 
germ-cells to body-cells. For while he originally 
supposed the fundamental distinction in kind to obtain 
as between the whole contents of a germ-cell and the 
whole contents of a somatic-cell, he now regards this 
distinction as obtaining only between the nucleus of 
a germ-cell and the nucleus of a somatic-cell. In 
other words, he regards the whole of a germ-cell, with 
the exception of its nucleus, as resembling the whole 
of any other cell, with the exception of z¢s nucleus. 
It is the nucleus of a germ-cell alone that contains 
germ-plasm : all the rest of such a cell being “ nutritive, 
but not formative.” 

This transference of the peculiar or hereditary 
powers of a germ-cell from the cell as a whole to 
the nucleus, necessitates certain emendations of the 
original theory of germ-plasm. In particular, the 
broad distinction between the whole contents of 
a germ-cell as “ germ-plasm,’ and the whole contents 


3006 6An Examination of Wetsmannism. 
7 


of a somatic-cell as “ somato-plasm,” is now discarded ; 
and in its stead we have all nuclear matter (whether 
of germ-cells or somatic-cells) comprised under the one 
denomination of “nucleo-plasm,” in contradistinction 
to all the other protoplasm of a cell, which is called 
“cytoplasm.” Hence Weismann now regards the 
cytoplasm of a germ-cell as identical with the cytoplasm 
of all other cells. Its function is merely that of 
“nourishing ” the nucleus, while, on the other hand, it 
is “controlled” by the nucleus as to its own growth, 
shape, size, and eventual division. 

But it is evident that the nucleo-plasm of a germ-cell 
must differ from the nucleo-plasm of a somatic-cell, in 
that it not only “controls” the growth, &c. of its own 
cell, but likewise presents all the additional characters 
peculiar to a germ-cell. That is to say, the nucleo- 
plasm of a germ-cell resembles the nucleo-plasm of 
a somatic-cell in that it is nourished by, and exercises 
control over, the cytoplasm of its own particular cell ; 
but it differs from the nucleo-plasm of a somatic-cell 
in admitting of fertilization, in the capability of 
reproducing an entire organism, in the endowing of 
that organism with all its hereditary characters, and, 
lastly, in providing for its own reproduction in the next 
generation. 

Thus it is evident, as Weismann puts it, that the 
nucleo-plasm of a germ-cell must be of zwo kinds— 
one being concerned with the formation and control of 
the germ-cell only, while the other has to do with the 
construction of an entire future organism, and the sub- 
sequent reproduction thereof. But not only so; for at 
each stage in the construction of this future organism, 
all the somatic-cells, as successively constructed, must 


Later Additions up to the year 1892. 31 


likewise contain nucleo-plasm in two kinds—one having 
to do only with the formation and control of its own 
‘individual cell, and the other having to do with the 
formation of the*future somatic-cells, which will have 
to follow in the course of ontogeny. Therefore, in 
order to designate this second kind of nucleo-plasm 
(whether in a germ-cell or a somatic-cell) Weismann 
borrows from Nageli the term “ idio-plasm 1,” or rather, 
I should say, he uses the term “nucleo-plasm ” when 
he is speaking of all the contents of a nucleus indis- 
criminately, while he uses the term “idio-plasm” when 
he has occasion to speak specially of the two kinds of 
nucleo-plasm now before us. 

Hence, the nuclear contents (nucleo-plasm) of every 
cell, whether germinal or somatic, present two sub- 
stances, which we may, in the absence of any better 
terms supplied by Weismann himself, respectively 
designate “idio-plasm-A” and “idio-plasm-B.” Idio- 
plasm-A is the substance which has to do only with 
the formation and control of the individual cell in 
which it resides, like a mollusc in its shell. Idio- 
plasm-B is the substance out of which future cells 
are to be formed and controlled, when in due course 
either of ontogeny or phylogeny this idio-plasm-B 
becomes converted into idio-plasm-A,—i. e., into each 
subsequently developing tissue or organism, as the case 
may be. I say ontogeny or phylogeny, and tissue 
or organism, because, where a germ-cell is concerned, 
idio-plasm-B is capable of reproducing entire organ- 
isms of its own and of subsequent generations; whereas, 


1 The meaning of this term, however, as originally used by Nageli, 
he so greatly changes to suit the requirements of his own theory, that 
I think it would have been better had he coined some new one. 


32 An Examination of Wetsmannism. 


in the case of all somatzc-cells, idio-plasm-B is capable 
only of reproducing, stage by stage, some greater or 
less number of the cells which are to construct the 
single organism of which they form a part. Or, other- 
wise expressed, in the particular case of a germ-cell 
idio-plasm-B is germ-plasm, and therefore is alone 
capable of producing an entire organism of somatic- 
cells, while it is likewise alone capable of reproducing 
successive organisms; for it alone contains the 
carriers of heredity’. 

Thus, idio-plasm-B of an unsegmented germ- 
nucleus is germ-plasm. But as soon as the germ- 
nucleus has undergone its first nuclear division, its 
nucleo-plasm is no longer germ-plasm, inasmuch as 
each of the half-portions is now no longer capable of 
reproducing an entire organism—unless it be in the 
case of identical twins. Similarly in the second nuclear 
division, each of the four resulting idio-plasms-B is 
still further removed from the pristine character of 

1 T think it is to be regretted that for this other kind of idio-plasm 
(i.e., idio-plasm-B) Weismann has not coined some distinctive name, 
or some distinctive prefix, such as that which he sometimes employs when 
speaking of the other kind (i.e., idio-plasm-A)—viz., ‘“ somatic-idio- 
plasm.” Also, the interchangeable manner in which he uses his term 
‘idio-plasm” with the term “nucleo-plasm,”’ is somewhat confusing 
(e.g., pp. 217, 219, 220, 250, 251, &c.). I may add that the word 
“plasm” in all its combinations apj:ears to me an unfortunate one, 
since it seems to betokenu a substance that can be see, instead of merely 


inferred. But, be this as it may, the following table of terms employed 
may be useful for ready reference :— 


Nucleo-plasm = the whole contents of the nucleus of any cell. 

Cytoplasm = all the other contents of any cell. 

Idio-plasm-A = that portion of nucleo-plasm which “ controls” a single 
cell. 

Idio-plasm-B = that portion of nucleo-plasm which is destined to 
construct future cells. 

Germ-plasm = undifferentiated idio-plasm-B, 


Somato-plasm = idio-plasm-A + cytoplasm. 





Later Additions up to the year 1892. 33 


germ-plasm ; and so on through all successive stages 
of segmentation. Hence these successive nuclear 
divisions must indicate a partitioning and re-par- 
titioning of the original idio-plasm-B (germ-plasm) 
into the idio-plasms-B severally distinctive of all the 
various cells of the soma. 

Now, it is evident that not a// the idio-plasm-B of 
a germ-cell which thus passes over into the nuclei of 
somatic-cells can be represented by the idio-plasm-B 
of those cells. At every stage of successive cell- 
formation a certain part of the original idio-plasm-B of 
the germ-cell must become the idio-plasm-A of somatic- 
cells distinctive of that stage. For, supposing that at its 
differentiation stage 99 the original germ-plasm (now 
somatic-idio-plasm-B of ggth stage) has reached a 
phase of ontogeny where the formation of tissue # has 
next to be followed by the formation of tissue 7, then 
there still remain the further differentiation.stages 101, 
102, 103, &c., to be provided for, which, when their time 
arrives, will go to form the still later tissues 0, p, g, &c. 
Consequently the idio-plasm-B of stage 100 cannot be 
all consumed in making the tissue x. There must be 
a residual portion which will afterwards be called upon 
to form successively the idio-plasm-A of 0, ~, g, &c. 
Where, then, is this residual portion of idio-plasm 
posited? Clearly it must be posited in the nuclei 
of z. Thus it is that, as we began by stating, all the 
nuclei of any given tissue z really contain two kinds of 
substance,—(1) their own idio-plasm-A, which was part 
of idio-plasm-B of the preceding tissue, #; and (2) the 
idio-plasm-B, which is destined to become idio-plasms- 
A of succeeding tissues 0,f, 7, &c. Thus it follows also 
that the more the original idio-plasm-B is differentiated 

D 


34. An Examination of Wetsmannism. 


into these successive formations of idio-plasms-A the 
less of it remains for further differentiation, till, at the 
last stage of ontogeny, all the original idio-plasm-B 
(germ-plasm)has been thus changed into idio-plasms-A 
severally distinctive of all the somatic-tissues a, b,c 
—X, y, 2,—save only the portion of it which has been 
carried through all these ontogenetic stages in a 
wholly wzdifferentiated condition, for the purpose of 
securing the phylogenetic production of the next gener- 
ation. And this, of course, is secured by the portion of 
undifferentiated germ-plasm in question being de- 
posited in the nuclei of germ-cells, at whatever stage of 
the ontogeny these may be formed. 

Finally, it is evident that, at each stage of the 
differentiation of idio-plasm-B into idio-plasms-A, 
the portion concerned must be capable of self-multi- 
plication to an almost incalculable extent,—yet this 
only as idio-plasm-B of the particular kind required for 
constructing the idio-plasm-A which is appropriate to 
the particular stage. Such is a necessary deduction 
from the terms of Weismann’s theory, inasmuch as we 
know that at each of the ontogenetic stages there is 
an incalculable multiplication of cells belonging to that 
stage—cells, the “cytoplasm” of which necessarily 
presupposes for its formation its own appropriate 
idio-plasm in both kinds, and thisin similarly increased 
quantities. 


From the above theory it follows that an explana- 
tion can be given of the healing of wounds (as in 
ourselves), of the regeneration of lost parts (as the 
limb of a newt), or even of the reproduction of an 
entire organism from a mere fragment of somatic- 


Later Additions up to the year 1892. 35 


tissue (as in the cases already alluded to at the com- 
mencement of this chapter—viz. the leaf of Begonia, 
portions of sea-anemones, jelly-fish, &c.). For in 
all these cases of repair, regeneration, and what may 
be called somatic reproduction, we have only to suppose 
that not all the idio-plasm-B of any given ontogenetic 
stage is consumed in the formation of that stage, and 
therefore that the residue is passed on to the later 
stages zz a latent condition. It will then be avail- 
able at any time to re-develop tissue corresponding 
to that particular stage, should that particular tissue 
happen to be lost by accident or disease. For example, 
if some of the idio-plasm-B of the very first onto- 
genetic stage, or true germ-plasm, should thus be 
passed on in an undifferentiated condition through 
the somatic-tissues subsequently formed at later onto- 
genetic stages, then we can understand why an extzre 
organism is reproduced from a fragment of these 
tissues—or of those among which particles of such 
residual and undifferentiated germ-plasm happen to 
be scattered. Similarly, if idio-plasm-B of the onto- 
genetic stage at which a limb is formed be not all 
consumed in constructing the limb, then the limb, 
if afterwards lost, will be re-constructed, although an 
entire organism will not be reproduced from a frag- 
ment of somatic-tissue. And similarly also with the 
mere repair of injuries, where the only overplus of 
idio-plasm-B is that of idio-plasm-B belonging to the 
very last stages of ontogeny. 

But, it is almost needless to observe, this kind of 
transmission of idio-plasm-B from one stage of on- 
togeny in an unaltered condition to subsequent stages, 
is not to be confused with the other kind of trans- 

D 2 


36 An Examination of Wetsmannism. 


mission previously referred to, whereby idio-plasm-B 
of one stage becomes successively transformed into 
the idio-plasms-A of successive stages. In the 
former case, at whatever stage of ontogeny the 
transmission may start from, the idio-plasm-B from 
that stage lies dormant, and is never destined to 
undergo further differentiation, unless the results of 
accident or disease should call upon it to do so. In 
the latter case, on the other hand, the idio-plasm-B 
of any given stage is passed on to the next stage 
for the express purpose of transforming itself into 
the idio-plasms-A of that and, in due order, of all 
subsequent stages. 


It will be observed that all this elaboration of the 
original theory of germ-plasm—an elaboration which 
is largely derived from the speculative writings of 
Nageli—serves no other purpose than that of indicating 
what Professor Weismann now regards as the most 
probable mode in which germ-plasm undergoes its 
modification into the various kinds of somatic-cells. 
For, inasmuch as the idio-plasms-B of all somatic-cells 
are originally derived from that of the germ-cell, and 
inasmuch as each expends its formative energies 
exclusively in constructing and controlling the cells 
which, as idio-plasms-A, they respectively inhabit, it 
is still the germ-plasm of the original germ-cell that 
is finally converted into the various tissues which 
together constitute the soma—notwithstanding that, 
in order thus to become transmuted into body-sub- 
stance, or somato-plasm,it must passthrough the sundry 
intermediate stages of idio-plasm-B, idio-plasm-A, and 
cytoplasm, of any given ontogenetic stage. Hence 


Later Additions up to the year 1892. 37 


I do not see that it makes any substantial difference to 
Weismann’s theory of heredity, whether we speak of 
germ-plasm being converted into ‘“ somato-plasm,” 
or into “idio-plasm” plus “ somatic-idio-plasm,” plus 
“cytoplasm.” But as Weismann himself thinks that 
it does make some great difference whether we adhere 
to his original generic term “somato-plasm,” or adopt 
his newer and more specific terms as just enumerated, 
I append zz extenso the most recent exposition of his 
views upon this subject ?. 

Before quitting this somewhat complicated addition 
to the original theory of germ-plasm, I must briefly 
allude to the descriptions and illustrations of karyo- 
kinesis which were given in Part lof Darwin and after 
Darwin, for the prospective benefit of any general 
readers who might afterwards be sufficiently interested 
in Weismann’s speculations to desire a statement of 
the main facts on which this further development of his 
theory rests. It seemed undesirable to burden the 
present volume with an account of recent investigations 
so well known to naturalists, while, on the other hand, 
it was clearly desirable that such an account should be 
given somewhere, if the speculations in question were 
to be rendered intelligible to anybody else. There- 
fore I must here request those of my readers who are 
not already acquainted with the matter to consult 
pp. 128-134 of Part I. It will there be seen how 
enormously complex are the visible processes which 
take place in the nucleus of a germ-cell (and likewise 
of a somatic-cell), preparatory. to its division; and 
therefore, supposing that the nucleus alone contains 
the material concerned in the phenomema of heredity, 

1 See close of Appendix. 


38 An Examination of Wetsmannism. 


it appears that no small corroboration is lent to Weis- 
mann s views by these histological observations. And, 
more particularly, if we suppose with him that the 
material in question is restricted to that portion of 
the segregating nuclear matter which is called the 
‘nuclear thread!,” in the formation of the “loops” 
or “rods” of this substance we seem to have pre- 
sented a visible expression of the marshalling of “the 
carriers of heredity,” and the successive passage of the 
originally generalized “ germ-plasm”’ of the germ-cell 
into the ever more and more specialized “nucleo- 
plasms” of the somatic-cells. Indeed, the new theory 
of heredity, when thus brought into relation with the 
new results of histological observation, appears so well 
to fit the latter, that one would be sorry to find 
the coincidence unmeaning, or the theory false. But, 
without passing any criticism, it is sufficient to note 
that the question whether or not the theory is true— 
and therefore correctly interprets the phenomena of 
karyokinesis—must depend chiefly on whether it 
be eventually proved that the “nuclear thread” is 
indeed the only part of a germ-cell, or even the 
only part of a tissue-cell, which is concerned in con- 
trolling the phenomena of heredity on the one hand, 
and of ontogeny on the other. Into this question, 
however, I do not propose to enter. It will be enough 
to assume, for the sake of argument, that Weismann’s 
view of the matter will eventually prove to be true. 
At the same time, we must remember that at present 
this view as to the nuclear thread being the sole 


1 See Part I, figs. 36, 37, and 38. The substance of this thread, in 
the various phases of its segmentation, is the ‘‘ chromatin,” as there 
depicted, and so called because it takes a stain better than other parts 
of the nucleus—thus showing some distinctive character. 


Later Additions up to the year 1892. 39 


repository of the material of heredity is merely hypo- 
thetical. 


We now arrive at the last of those features in 
Weismann’s theory of heredity, the importance of 
which necessitates mention in such a mere statement 
of the theory as the present chapter is concerned 
with. 

According to Weismann’s own view of his theory, 
two objections have to be met. In the first place, 
there is the objection that all individuals whzch are 
born of the same parents are not exactly alike, as the 
theory might have expected they would be, seeing that 
the admixture of identical germ-plasms has been con- 
cerned in the formation of the whole progeny. In 
the second place, and quite apart from this objection, 
there is the difficulty that, if every act of fertilization 
essentially consists in a fusion of one mass of germ- 
plasm belonging to a male germ-cell with another mass 
belonging to a female germ-cell, at each generation 
the mass of germ-plasm contained in an egg-cell 
must be doubled—with the result that ova must 
progressively increase in size during the course 
of phylogeny. But ova do not thus progressively 
increase in size. Therefore, if the imperishable nature 
of germ-plasm is to be theoretically sustained, it 
is necessary to show some means whereby ova 
and spermatozoa are able to get rid of at least 
one half of their respective germ-plasms in each 
generation—i.e., before each act of impregnation. 
Weismann meets both these difficulties by an appeal 
to the following facts. 

It is well known that the ripe ovum extrudes two 


40 An Examination of Wetsmannism. 


minute particles of protoplasmic substance, which are 
called polar bodies?!. These both proceed from the 
nucleus of the ovum, but are not formed simul- 
taneously. For the first polar body is really one 
half of the original nucleus of the cell, and therefore 
is formed by the first segmentation of this nucleus. 
The second polar body, on the other hand, is one half 
of the remaining nucleus, and is similarly formed 
by the second segmentation. Hence, when both 
polar bodies have been extruded from the ovum, only 
one quarter of the original nuclear matter remains. So 
far, of course, the facts prove too much for Weis- 
mann’s theory, because the theory wants to get rid of 
only one half of the original nuclear matter before 
impregnation, zf all the nuclear matter be germ-plasm. 
Therefore Weismann concludes that all the original 
nuclear matter of the ripe ovum is zot germ-plasm, 
but that only one half of it is so, while the other half— 
or that half which goes to constitute the first polar 
body—is idio-plasm-A, which, as we have already 
seen, the egg-cell shares in common with all other 
cells. It is merely “ovogenetic”: its function is that 
of constructing the ovum, guwdé@ cell: it has nothing 
whatever to do with the germ-plasm which the 
particular cell contains. Therefore, having discharged 
its function of constructing this cell, it is itself dis- 
charged from the cell as the first polar body. 

The nucleus of the fully-formed ovum having thus 
got rid of all its superfluous idio-plasm-A by throwing 
off the first polar body, is supposed henceforth to 


* For an account of the formation and expulsion of these bodies, see 
Part I, pp. 125-6. There is now no longer any doubt touching the 
statement there made as to the male-cell likewise parting with some of 
its nuclear substance prior to fertilizing the female. 


Later Additions up to the year 1892. 41 


consist of pure germ-plasm (i.e., of idio-plasm-B 
belonging to the first ontogenetic stage), and one half 
of this is next got rid of by the second segmentation 
in the form of the second polar body. Therefore, 
according to the theory and so far as the problems 
of heredity are concerned, we need not any further 
trouble ourselves about the first polar body. But it 
will at once be seen that by the interpretation which 
Weismann puts upon the second polar body, and 
also, of course, upon the extrusion of some of its 
nuclear matter by the male cell, he meets both the 
difficulties against his theory of germ-plasm which 
we are now engaged in considering. 

That he thus meets the second of those difficulties— 
.1,e., concerning the otherwise perpetual accumulation 
of germ-plasm—is evident without explanation. That 
he likewise meets the first—i.e., concerning the non- 
resemblance of individuals born of the same parents— 
is scarcely less evident. For it is hardly conceivable 
that such a complex mass of germ-plasms as the 
nucleus of a fertilized ovum must be could ever 
present in any two eggs precisely the same propor- 
tional representation of the “carriers of heredity,” 
after one half of each set had been thus discharged 
from each egg. Therefore, if the second polar body 
removes from each egg one half of the ancestral germ- 
plasms, “every egg will contain a somewhat different 
combination of hereditary tendencies, and thus the 
offspring which arise from the different germ-cells of 
the same mother can never be identical}. 

Such, then, is Weismann’s theory of the physio- 


1 In the case of identical twins, both are probably always produced 
from the same ovum. 


42 An Examination of Wetsmannism. 


logical meaning of polar bodies. And as the bearing 
of this particular theory on his more general theory 
of heredity does not appear to me a vitally intimate 
one, I think my subsequent examination of the main 
theory will be simplified if I now proceed at once 
to an examination of the subordinate one. For by 
doing this I shall hope to show that the bearings just 
mentioned are of much less importance than he repre- 
sents them to be ; and, therefore, that we may hereafter 
proceed to consider his theory of heredity without any 
special reference to his theory of polar bodies. 

To begin with, as regards the first polar body, one 
would like to know more clearly why it is necessary 
that this residuum of merely “ ovogenetic idio-plasm ” 
(or idio-plasm-A of the egg-cell) has to be got rid 
of before the germ-plasm can proceed to discharge 
its physiological functions. Seeing that both these 
(hypothetically) very different materials occur in the 
self-same nucleus, some very delicate mechanism must 
be needed for their separation ; and it is not apparent 
why such a mechanism should have been evolved, 
rather than what would have been the simpler plan of 
adapting the germ-plasm to hold its own against the 
idio-plasm-A, even if one could see that any inter- 
ference between these very different substances is in 
any way probable. For my own part, at all events, 
I cannot see why this microscopical atom of ‘ ovo- 
genetic idio-plasm” should not simply be left to 
be absorbed among the millions of cells that after- 
wards go to form the foetus. 

Again, asregards the second polar body, Weismann’s 
theory of it is framed to explain, (a) how the excess of 
germ-plasm is got rid of in each ontogeny, and (4) why 


Later Additions up to the year 1892. 43 


the offspring of the same parents do not all precisely 
resemble one another. These, be it observed, are the 
only two functions which Weismann’s theory of polar 
bodies subserves in relation to his theory of germ-plasm. 
But, it appears to me, neither of these functions is 
necessary, in so far as any requirements of the latter 
theory are concerned. For surely, polar bodies or no 
polar bodies, there is already a mechanism at work in 
each ontogeny which is of itself sufficient to discharge 
both these functions, and so to anticipate both the 
supposed difficulties which the subsidiary theory is 
adduced to meet. The very essence of ontogeny, 
as a process, itself consists in a continuous succession 
of nuclear divisions—and this not only as regards 
somatic-cells, but also as regards germ-cells. Now, in 
the great majority of organisms, there is an infinitely 
greater number of germ cells (both male and female) 
than can possibly be required either for the purpose 
of getting rid of any excess of germ-plasms in the 
nucleus of each cell, or of preventing the germ-plasms 
of any one germ-cell precisely resembling those of 
any other. If every plant or animal produced only 
a single female-cell or a single male-cell, then indeed 
we might require from Professor Weismann a demon- 
stration of some special mechanism to secure the ex- 
pulsion of half its ancestral germ-plasms ; since other- 
wise the single female-cell or male-cell would have to 
increase its dimensions in each successive generation. 
But, as matters actually stand, nature seems to have 
made much more than ample provision for prevent- 
ing the undue accumulation of ancestral germ-plasms 
in any individual germ-cell, by enormously multiply- 
ing, through continuous division and subdivision, the 


44. An Examination of Weismannism. 


number of germ-cells in each ontogeny. And simi- 
larly, of course, as regards the different aggregations of 
ancestral germ-plasms which are left for distribution 
among these innumerable germ-cells. “If one group 
of ancestral germ-plasms is expelled from one egg, 
and a different group from another egg, it follows 
that no two eggs can be exactly alike as regards their 
contained hereditary tendencies.” Granted; but this 
consideration applies equally to the original segre- 
gation of germ-plasms in the multiplying eggs of each 
ontogeny—for it follows from the theory of germ- 
plasm that the most primitive egg-cell in each ontogeny 
must have contained all the ancestral germ-plasms 
which are afterwards distributed among its innumer- 
able progeny of egg-cells. And, as far as the facts of 
“ individual variation’ are concerned, I do not see why 
the differential partitioning of “ancestral idio-plasms” 
should be any better secured by nuclear division ot 
a mature germ-cell than by that of an immature. 
Less so, indeed; for the wonder is that during 
the many-thousand-fold division of an immature 
ovum so precise a distribution of these “ancestral 
idio-plasms” is maintained, as is proved to be main- 
tained (on the theory of germ-plasm) by the facts of 
heredity. 

However, Weismann takes a widely different view of 
the matter. For while he allows that “ such an early 
reducing division would offer advantages in that 
nothing would be lost, for both the daughter nuclei 
would (? might) become eggs, instead of one of 
them being lost as a polar body ’—while he allows 
this, he nevertheless rejects the possibility of “such an 
early reducing division.” But I do not see that the 


Later Additions up to the year 1892. 45 


reasons which he assigns for this rejection of it are 
adequate. 

First, he says that if this were the way in which the 
superfluous germ-plasm of each generation were got 
rid of, far too much provision has been made for the 
purpose,—seeing that the practically indefinite number 
of nuclear divisions which the immature germ-cells 
undergo would cause a much “greater decrease of 
the ancestral idio-plasms of each than could afterwards 
be compensated by the increase due to fertilization.” 
But this rejoinder is of cogency only if it be supposed 
that at each nuclear division of an immature ovum, 
“the ancestral idio-plasms” (germ-plasm) are in- 
capable of the power of self-multiplication which soon 
afterwards becomes one of its most essential characters. 
Why, then, should we suppose this substance to be 
totally incapable of increase in the multiplying ova of 
ontogeny, when at the same time we are to suppose 
the same substance capable of any amount of increase 
in the multiplying ova of phylogeny ? To this obvious 
question no answer is supplied: in fact the question 
is not put. 

Secondly, Weismann says that in parthenogenetic 
ova onlyone polar body is extruded. Thishe regards as 
equivalent to the first polar body ofa fertilizable ovum 
(i.e., as composed of ovogenetic nuclear substance) ; 
and hence he argues that the second polar body 
of a fertilizable ovum must be regarded as composed 
of germ-plasm. But even supposing that he is right 
as to the fact that parthenogenetic ova invariably 
extrude but one polar body, his argument from this 
fact would only be available after we had already 
accepted his view touching the character of the 


46 An Examination of Wetsmanutsm. 


second polar body. So long as this view is itself the 
subject of debate, he cannot prove it by the fact in 
question. In other words, unless we have already 
agreed that the second polar body has the function 
which Weismann assigns to it, we cannot accept the 
fact which he adduces as furnishing any evidence of 
his view touching the function of the second polar 
body. 

For these reasons I cannot see that the subordinate 
theory of polar bodies is required in the interests of 
the general theory of germ-plasm. The difficulties 
which it is adduced to meet do not appear to me to 
be any difficulties at all. Therefore, in now proceeding 
to consider what in my opinion are the real difficulties 
which lie against the major theory of germ-plasm, I. 
shall not again allude to the minor—and, in this con- 
nexion, superfluous—theory of polar bodies. 

Such, then, is Professor Weismann’s theory of 
heredity in its original and strictly logical form. In 
the course of our examination of it which is to 
follow in Chapter III and IV, we shall find that in 
almost every one of its essential features, as above 
stated, the theory has had to undergo—or is demon- 
strably destined to undergo—someradical modification. 
But I have thought it best to begin by presenting 
the whole theory in its completely connected state, 
as it is in this way alone that we shall be able to 
disconnect what I regard as the untenable parts from 
the parts which still remain for investigation at the 
hands of biological science. Such, indeed, is the only 
object of my “ Examination of Weismannism.”’ For, 
rightly or wrongly, it appears to me that the unques- 
tionable value of his elaborate speculations is seriously 


Later Additions up to the year 1892. 47 


discounted by certain oversights with regard to 
matters of fact, and not a few inconsistencies touching 
matters of theory. In displaying both these defects, 
I am not without hope that the result may be that 
of inducing Professor Weismann so to modify his 
system of theories as to strengthen the whole by ' 
removing its weaker parts. 


GinboMe ies JUG 


WEISMANN’S THEORY OF HEREDITY (1891). 


WE now proceed to examine Weismann’s theory of 
germ-plasm, and as this in its various developments 
has now become a highly complex theory, we had 
best begin by marking out the lines on which the 
examination will be conducted. 

As I have already pointed out, the Weismannian 
system is not concerned only with the physiology 
of reproduction: it is concerned also—and in an even 
larger measure—with the doctrine of descent. The 
theory of germ-plasm as a whole is very much more 
than a theory of heredity; it is a new theory of 
evolution. The latter, indeed, is deduced from the 
former; but although the two are thus intimately 
related, they are nevertheless not mutually dependent. 
For the relationship is such that the new theory of evo- 
lution stands upon the basis supplied by the new theory 
of heredity, and although it follows from this that 
if the latter were disproved the former would collapse, 
it does not follow that if the former were to be found 
untenable the latter must necessarily be negatived. 
Hence, for the sake of clearness, and also for the 
sake of doing justice to both theories, we had best 
deal with them separately. The present chapter, then, 


Weismann's theory of Feredity (1891). 49 


will be devoted to examining Weismann’s theory of 
heredity, while the ensuing chapter will be concerned 
with his sequent theory of evolution. 

Again, Weismann’s theory of heredity stands on 
his fundamental postulate—the continuity of germ- 
plasm; and also on a fact well recognized by all other 
theories of heredity, which he calls the stability of 
germ-plasm. But his sequent theory of evolution 
stands not only on this fundamental postulate. and on 
this well-recognized fact; it requires for its logical 
basis two further postulates—viz., that germ-plasm 
has been perpetually continuous “ since the first origin 
of life,’ and wxalterably stable “since the first origin 
of sexual propagation.” That these things are so, 
a very few words will be sufficient to prove. 

Any theory of heredity which supposes the material 
of heredity to occupy a more or less separate “sphere ” 
of its own, is not obliged further to suppose that this 
material has afways been thus isolated, or even that 
itis now zzvariably so. There have been one or two 
such theories prior to Weismann’s, and they were 
founded on the well-known fact of congenital characters 
being at any rate much more heritable than are 
acquired characters. But it has not been needful for 
these theories to assume that the “continuity” thus 
postulated has been perpetual/y unbroken. Even if it 
has been frequently to some extent interrupted, all 
the facts of heredity could be equally well comprised 
under such theories—and this even if it be supposed 
that acquired characters are but rarely, or never, 
transmitted to progeny. For, in as far as the con- 
tinuity may have been interrupted, it does not follow 
that the acquired characters (body-changes), which by 

E 


50 An Examination of Wetsmannism. 


hypothesis caused the interruption, must be inherited 
by progeny exactly as they occurred in the parents. 
Or, in other words and adopting Weismann’s ter- 
minology, so far as the facts of heredity are concerned, 
there is no reason why germ-plasm should not 
frequently have had its hereditary qualities modified 
by some greater or less degree of commerce with 
somatic-tissyes, and yet never have reproduced in pro- 
geny the identical acquired characters which caused 
the modification of germ-plasm in the parents: some 
other and totally different characters might with equal 
—or even more—likelihood have been the result, as we 
shall see more clearly a few pages further on. Why, 
then, does Wcismann so insist upon this continuity of 
germ-plasm as perpetual “ since the origin of tife” ? It 
appears to me that his only reason for doing so is 
to provide a basis, not for his theory of heredity, but 
for his additional theory of evolution. It is of no 
consequence to the former that germ-plasm should 
be regarded as thus perpetual, while it is of high 
importance to the latter that the fundamental postulate 
of continuity should be supplemented by this further 
postulate of the continuity as thus perpetual. 
Similarly as regards the postulate of the stability 
of germ-plasm as absolute. It is enough for all the 
requirements of Weismann’s theory of heredity that 
the material basis of heredity should present a merely 
high degree of stability, such as the facts of atavism, 
degeneration, &c. abundantly prove that it possesses. 
For his sequent theory of evolution, however, it is 
necessary to postulate this stability as absolute “ since 
the first origin of sexual reproduction.” Other- 
wise there would be no foundation for any of the 


Weesmann's theory of Feredity (1891). 51 


distinctive doctrines which go to constitute this 
theory. 

It may not be immediately apparent that Weis- 
mann’s theory of heredity is not per se concerned 
with either of these two additional postulates of the 
continuity of germ-plasm as perpetual, and the stability 
of germ-plasm as absolute; while both are logically 
necessary to his further theory of evolution. On this 
account, and also for the sake of clearness in all 
that is to follow, we had best begin by comparing 
his theory of heredity with those of his principal 
predecessors—Darwin and Galton. 


For the purposes of this comparison we may start by 
again alluding to the fact, that even in the multicellular 
organisms reproduction is not confined to the sexual 
methods. Many kinds of invertebrated animals will 
reproduce entire organisms from the fragments into 
which a single organism has been chopped: plants 
of various kinds can be propagated indefinitely by 
cuttings, grafts, and buds, or even by leaves, as we 
have already observed in Chapter I. Now, when 
the whole organism is thus reproduced from a severed 
portion of somatic-tissue, it reproduces its sexual 
elements. Whence, then, in such cases are these 
elements derived? Obviously they are not derived 
immediately from the sexual organs—or even from 
the sexual cells—of their parents: they are derived 
from the somatic-cells of a single parent, if we choose 
to retain this term; and therefore, as Strasburger 
pointed out soon after Weismann’s theory was pub- 
lished, it seems as if such facts are in themselves 
destructive of the theory. How, then, does Weismann 

KE 2 


52 An Examination of Wetsmannism. 


meet them? As we have already seen in Chapter II, 
he meets them in the only way they can be met on 
the lines of his theory—viz., by those newer amend- 
ments of his theory which suppose that in all these 
cases the germ-plasm is of confined to the specially 
sexual cells, but occurs also in the nuclear substance 
of those somatic-cells which thus prove themselves 
capable of developing into entire organisms. In 
other words, the sexual elements which develop 
during what I have previously called this “somatic 
reproduction” of multicellular organism, are supposed 
to be derived from the sexual cells of ancestors, not 
indeed immediately (for this they plainly are not), 
but mediately through the somatic-tissues of their 
a-sexual parent. Now, in view of this extension, the 
theory of germ-plasm becomes somewhat closely 
allied to that of pangenesis. FFor example, when the 
fragment of a leaf of Legonza is laid upon moist soil, 
there strikes root, and grows a new Segonza plant 
capable of sexual reproduction, Darwin supposes the 
explanation to be that what he calls “formative 
material” occurs inall cells of the leaf, while Weismann 
supposes the explanation to be that what he calls 
“serm-plasm”’ occurs in all—or at any rate in most — 
of the cells of the leaf. So that, except as regards the 
terms employed, the two theories are identical in their 
mode of viewing this particular class of phenomena. 
Moreover by thus allowing, in his second essay on 
Heredity, that germ-plasm need not be restricted to 
the specially sexual cells, but in some cases, at any 
rate +, may occur distributed in full measure of repro- 


' We have no means of estimating exactly the proportional number 
of cases in which this is possible, either among the lower or the higher 


Wersmann's theory of Heredity (1891). 53 


ductive efficiency throughout the general tissues of 
the organism, Weismann cannot refrain from taking 
the further step of supposing that the germ-plasm, 
like the gemmules of Darwin, is capable of any 
amount of multiplication zz the general cellular tissues 
of plants—seeing that plants can be propagated by 
cuttings, buds, &c.,indefinitely. And this, as we have 
seen, Professor Weismann, in his second essay, does 
not shrink from doing. Moreover, although I cannot 
remember that he has anywhere expressly said so, it 
is obvious that the allied phenomena of regeneration 
and repair admit of explanation by his hypothesis 
of “ontogenetic grades,” after the manner already 
stated in Chapter II. Indeed, it is evident that in 
no other way can these phenomena be brought 
within the range of his theory. But from this it 
follows that not only in the case of organisms which 
are capable of somatic reproduction is the formative 
nucleo-plasm (idio-plasm-B) diffused throughout the 
somatic-tissues: on the contrary, it must be wzzver- 
sally diffused throughout a// the somatic-cells of all 
living organisms; and whether as it there occurs it is 
capable of reproducing entire organisms, single organs, 
plants; but it is certainly much greater than Weismann supposes. 
“ How is it that all plants cannot be reproduced in this way?” he asks, 
and then adds,—‘‘ No one has ever grown a tree from the leaf of a lime 
or an oak, or a flowering plant from a leaf of the tulip or the 
convolvulus.” But I am told by botanists that the only reason why 
the phenomenon thus appears to be a rare one, is because it is not 
worth anybody’s while to grow plants in this way at a necessarily 
unsuitable season of the year. Thus, the Rev. George Henslow 
writes me:—‘‘ The fact is that azy plant will reproduce. itself by its 
leaves, provided that the cells be ‘embryonic,’ (i.e., the leaf not 
too near its complete development), and that it be not too ¢hzn, 


so as to provide enough nutriment for the bud to form till it has 
roots.” 


54. An Examination of Wersmanuism. 


single tissues, or a mere cicatrix, depends only on 
the “ontogenetic grade” of differentiation which 
this diffused nucleo-plasm has (or has not) previously 
undergone. Moreover, as we have already seen, at 
whatever ontogenetic grade of differentiation it may 
be present in a given somatic-tissue, it must there be 
capable of indefinite self-multiplication. Therefore, 
in all these respects this “formative nucleo-plasm ” (or 
idio-plasm—B) of Weismann precisely resembles the 
“ formative material’ (or gemmules) of Darwin. 
Lastly, as De Vries has pointed out?, there must 
be at least as many divisions and subdivisions in 
the substance of germ-plasm, as there are differences 
between the somatic organs, tissues, and even cells, 
to which germ-plasm eventually gives rise—no matter 
through how many ontogenetic grades of idio-plasm 
it may first have to pass. Or, in other words, we must 
accept, as the material basis of heredity, ultimate 
particles? of germ-plasm, which are already differen- 
tiated into as many diverse categories as there are 
differences between all the constituent parts of the 
resulting soma; for, as shown in the Appendix, no 
change in the facts of the case has been shown by 
simply changing the original term “ germ-plasm ” into 
“idio-plasm,’ wherever the phenomena of ontogeny 
are concerned. It may be convenient, for the sake of 
presenting newer additions to the theory, to restrict 
the term “germ-plasm” to “ idio-plasm of the first 
ontogenetic stage”; but as idio-plasms of all subse- 


' Intracellulare Pangenesis, 8. 55. 

2 I employ the term “particles,” instead of ‘‘ molecules,” because 
although Weismann and his followers seem to prefer the latter term, 
I can scarcely imagine that they intend to use it in its original, or 
chemical, sense. 


Wetsmann's theory of Fleredity (1891). 55 


quent ontogenetic stages are supposed to be ultimately 
derived from this idio-plasm of the first stage, it is 
evident that the particulate differences in question 
must already have been present in the so-called 
“undifferentiated idio-plasm of the first ontogenetic 
stage.” Unless we are to have a mere juggling with 
words, we cannot put into our successive idio-plasms 
any particles of kinds differing from those which are 
contained in the original germ-plasm. Therefore I 
say that, notwithstanding this change of terminology, 
Weismann must continue to assume, as the material 
basis of heredity, ultimate particles of germ-plasm 
which are already differentiated into as many diverse 
categories as there are differences between the parts 
of the resulting soma—although, of course, these 
ultimate particles need not be nearly so numerous 27 
each of their categories as they afterwards become by 
self-multiplication while forming each of the resulting 
tissues. 

But this is precisely what the theory of pangenesis 
supposes; so that I see no reason why these ultimate 
particles of germ-plasm should not be regarded as 
“oemmules,’ so far as their szze, number, and function 
are concerned. In point of fact, they differ from 
gemmules only in respect to their orvzgzz: they are 
not particles derived from somatic-cells of the preceding 
generation, but particles derived from germ-plasm of 
the preceding generation. Or, to state the difference 
in another form, if we regard the sexual elements as 
constituting the physiological centre of the organism, 
then the theory of germ-plasm supposes these ultimate 
carriers of heredity to originate at this centre, and 
then to travel centrifugally ; while the theory of pan- 


56 An Examination of Wetsmannism. 


genesis supposes them to originate at the periphery. 
and then to travel centripetally. 

This point of difference, however, arises from the 
deeper ones, which—having now exhausted the points 
of agreement—we must next proceed to state. 

If, as we have seen, ‘formative material” and 
“serm-plasm” agree in being particulate ; in consti- 
tuting the material basis of heredity; in being mainly 
lodged in highly specialized, or germinal, cells; in 
being nevertheless also distributed throughout the 
general cellular tissues, where they are alike concerned 
in all processes of regeneration, repair, and a-sexual 
reproduction; in having an enormously complex 
structure, so that every constituent part of the future 
organism is already represented in them by corre- 
sponding particles; in being everywhere capable of a 
virtually unlimited multiplication, without ever losing 
their hereditary endowments ; in often carrying these 
endowments in a dormant state through a number of 
generations, until at last they re-appear again in what 
we recognize as reversions to ancestral characters ;— 
if in all these most important respects the two sub- 
stances are supposed to be alike, it may well appear 
at first sight that there is not much room left for 
any difference between them. And, in point of fact, 
the only difference that does obtain between them 
admits of being stated in two words,—Continuity, 
and Stability. Nevertheless, although thus so few in 
number, these two points of difference are points of 
great importance, as I will now proceed briefly to 
show. 

If the substance which constitutes the material 
basis of heredity has been perpetually continuous, in 


Wetsmann's theory of Heredity (1891). 57 


the sense of never having had any of its hereditary 
endowments in any way affected by the general body- 
tissues in which it resides, the following important 
consequences, it will be remembered, arise. The 
process of organic evolution must have been exclusively 
due to a natural selection of favourable variations 
occurring within the limits of this substance itself; 
and therefore the so-called Lamarckian factors can 
never have played any part at all in the evolution of 
any but the unicellular organisms. Onthe other hand, 
if this substance has not been thus perpetually con- 
tinuous, but more or less formed anew at each ontogeny 
by the general body-tissues in which it resides, natural 
selection has probably been in some corresponding 
degree assisted in its work of organic evolution by the 
Lamarckian factors, with the result that the experi- 
ences of parents count for something in the congenital 
endowments of their offspring. So much for the 
first of the two differences between germ-plasm and 
gsemmules, or the difference which arises from the 
perpetual continuity of germ-plasm. 

Touching the second difference, or that which arises 
from the absolute stability of germ-plasm, it will be 
remembered how from this character there arises 
another important chain of consequences. Namely, 
individual variations of the congenital kind can only 
be due to admixtures of different masses of germ- 
plasm in every act of sexual fertilization; natural 
selection is therefore dependent, for the possibility 
of its working, upon the sexual methods of propa- 
gation ; hence, natural selection is without any juris- 
diction among the unicellular organisms, where the 
Lamarckian factors hold exclusive sway ; and hence, 


58 An Examination of Wetsmannism. 


also, the multicellular organisms are ultimately depen- 
dent upon this absolute stability of their germ-plasm 
for all the progress which they have made in the 
past, as well as for any progress which they may be 
destined to make in the future. 

Thus we see that the two points of difference 
between germ-plasm and gemmules are not merely 
of great importance as regards the particular problem 
which is presented by the phenomena of heredity: 
they are of still greater importance as regards 
the general theory of evolution. For if these two 
qualities of perpetual continuity and absolute sta- 
bility can be proved to belong to the material basis 
of heredity, the entire theory of evolution will have 
to be reconstructed from its very foundation—and 
this quite apart from the more special question as 
to the transmission of acquired characters. There- 
fore we shall presently have to consider these two 
alleged qualities with the care that they demand, as 
having been seriously suggested by so eminent a 
naturalist as Professor Weismann. But, before pro- 
ceeding to do so, I must briefly compare his theory 
with that of Mr. Galton. 

“Stirp”’ resembles both “germ-plasm” and “ gem- 
mules” in all the respects which have above been 
named as common to the two latter. But it differs 
from gemmules and further resembles germ-plasm 
in all the following particulars. It is derived from 
the stirp of proceeding generations, and constitutes 
the sole basis of heredity. Only a part of it, however, 
is consumed in each ontogeny—the residue being 
handed over to “contribute to form the stirps of 
the offspring,” where it undergoes self-multiplication 


Weismann's theory of feredity (1891). 59 


at the expense of the nutriment supplied to it from 
the somatic system of the offspring, and so on through 
successive generations Again, stirp is concerned in 
all processes of regeneration and repair, in the same 
centrifugal manner as germ-plasm is so concerned. 
Furthermore, the influence of sexual propagation 
in the blending of hereditary qualities of the stirp 
is recognized, while the principle of panmixia, or the 
cessation of selection, is entertained, and shown to 
invalidate the evidence of pangenesis which Darwin 
derived from the apparently transmitted effects of 
use and disuse in our domesticated animals!. Lastly, 
it is clearly stated that on the basis supplied by 
this “theory of heredity,” it becomes logically pos- 
sible to dispense with the Lamarckian principles 
wz toto, leaving natural selection as the sole known 
cause of organic evolution through a perpetual con- 
tinuity of stirp, together with individual variations of 
the same, whether by sexual admixture or otherwise. 

So far, then, there is not merely resemblance, but 
virtual identity, between the theories of stirp and 
gserm-plasm. Disregarding certain speculative details, 
the coincidence is as complete as that between 
a die and its impress. But although the two 
theories are thus similar in dogzcal construction, they 
differ in their interpretations of dzological fact. ‘That 
is to say, although Galton anticipated by some ten 
years all the main features of Weismann’s theory of 
heredity”, and showed that, as a matter of form, it was 

1 This principle will be considered at some length in my next 
volume. 

? Galton first published his theory in 1872 (Proc. R. S., No. 136), 


but presented it in a more complete form three years later (Contemporary 
Review, Dec. 1875, and Journl. Anthropol. [nst., 1875). 


60 An Examination of Wetsmanntsm. 


logically intact, he refrained from concluding on this 
account that it must be the true theory of heredity. 
He argued, indeed, that in the main it was probably 
the true theory ; but he guarded his presentation of 
it by not undertaking to deny that there might 
still be some degree of intercommunication between 
the material basis of heredity in stirp, and the 
somatic tissues of successive organisms. The con- 
struction of a theory which, as a matter of theory, 
could dispense with the Lamarckian principles zz éoZo, 
was seen to be a very different thing from proving, 
as a matter of fact, that these principles are non- 
existent—and this, even though it was seen that 
a recognition of the principle of panmixia must be 
taken to have considerably attenuated the degree of 
their operation as previously estimated by Darwin in 
the theory of pangenesis. In short, after pointing out 
that the doctrine of stirp might very well adopt 
the position which about a decade later was adopted 
by the doctrine of germ-plasm—namely, that of 
altogether supplanting the doctrine of gemmules,— 
Galton allowed that this could be done only as 
a matter of formal speculation ; and that, as a matter 
of real interpretation of the facts of nature, it seemed 
more judicious to stop at modifying the doctrine of 
gemmules, by provisionally retaining the hypothesis 
of gemmules, but assigning to their agency a greatly 
subordinate vé/e. Or to quote his own words :— 


The conclusion to be drawn from the foregoing arguments is, 
that we might almost reserve our belief that the structural [i.e., 
““somatic”’| cells can react on the sexual elements at all, and 
we may be confident that at the most they do so in a very faint 
degree; in other words, that acquired modifications are barely, 


Wetsmanun's theory of Feredity (1891). 61 


if at all, inherited, in the correct sense of that word. If they 
were not heritable, then the second group of cases [i.e., those of 
acquired as distinguished from congenital characters] would 
vanish, and we should be absolved from all further trouble; 
if they exist, in however faint a degree, a complete theory of 
heredity must account for them. I propose, as already stated, 
to accept the supposition of their being faintly heritable, and to 
account for them by a modification of Pangenesis '. 


Seeing, then, that Galton did not undertake to 
deny a possibly slight influence of somatic-tissucs 
on the hereditary qualities of stirp, it follows that 
he did not have to proceed to those drastic modi- 
fications of the general theory of descent which 
Weismann has attempted. Stirp, like germ-plasm, 
is continuous; but, unlike germ-plasm, it is not 
necessarily or absolutely so. Again, stirp, like germ- 
plasm, is stable; yet, unlike germ-plasm, it is not 
perpetually or unalterably so. Hence we hear nothing 
from Galton about our having to explain the un- 
likeness of our children to ourselves by variations 
in our protozoan ancestors; nor do we meet with 
any of those other immense reaches of deductive 
speculation which, in my opinion, merely disfigure 
the republication of stirp under the name of germ- 
plasm. 

Now, I allude to these, the only important points of 
difference between stirp and germ-plasm, for the 
sake of drawing prominent attention to the fact that it 
makes a literally immeasurable difference whether we 
suppose the material basis of heredity to be fer- 
petually continuous and wralferably stable, or whether 
we suppose that it is but /avgely continuous and highly 


Journ, Anthropol. Inst, 1875, p. 346. 


62 An Examination of Wetsmannism. 


stable. In the former case, all the far-reaching 
deductions which Weismann draws with reference to 
the general theory of descent—or apart from the 
more special problem of heredity—follow by way 
of logical consequence. In the latter case, there is 
no justification for any such deductions. For, no 
matter how faintly or how fitfully the hereditary 
qualities of the material in question may be modified 
by the somatic-tissues in which it resides, or by 
the external conditions of life to which it is exposed, 
these disturbances of its absolute stability, and these 
interruptions of its perpetual continuity, must cause 
more or less frequent changes on the part of its 
hereditary qualities—with the result that specific or 
other modifications of organic types need not have 
been solely due to the varying admixture of such 
material in sexual unions on the one hand, or to the 
unassisted power of natural selection on the other. 
Numberless additional causes of individual variation 
are admitted, while the Lamarckian principles are 
still allowed some degree of play. And although 
this is a lower degree than Darwin supposed, their 
influence in determining the course of organic evolu- 
tion may still have been enormous; seeing that their 
action, in whatever measure it may be supposed 
to obtain, must always have been cumulative on the 
one hand, and directive of variations in adaptive 
lines on the other. Or, as Galton himself observes, 
in the passage already quoted, ‘‘ if they exist, 27 how- 
ever faint a degree, a complete theory of heredity 
must account for them.” He saw, indeed, that a most 
inviting dogzal system could be framed by denying 
that they can ever exist in any degrce—or, in 


Wersmann's theory of Heredity (1891). 63 


other words, by supposing that stirp was exactly 
the same as what was-afterwards called germ-plasm, 
in that it always occupied a separate “sphere” of 
its own, where its continuity has been uninterrupted 
“since the first origin of life”’ But Galton was not 
seduced by the temptation to construct an ideally 
logical system; and he had what I regard as the 
sound judgement to abstain from carrying his theory 
of stirp into any such transcendental “sphere” as that 
which is occupied by Weismann’s theory of germ- 
plasm, in relation to the general doctrine of descent. 


There is, then, a vast distinction between any 
theory of heredity which postulates the material of 
heredity as highly stable and largely continuous, and 
Weismann’s theory, which postulates this material as 
absolutely stable and perpetually continuous. But 
we must next take notice that Weismann himself has 
not kept this distinction in view with the constancy 
which we should have expected from so_ forcible 
a thinker. On the contrary, although in the con- 
struction of his theory of evolution he never fails 
to press the postulates of absolute stability and per- 
petual continuity to their logical conclusions in the 
various doctrines above enumerated (pp. 57-58), when 
engaged on his more special theory of heredity he 
every now and then appears to lose sight of the 
distinction. Indeed, he occasionally makes such large 
concessions with regard to both these postulates, 
that, were they to be entertained, the occupation of 
his critics would be gone: his theory of heredity 
would become converted into Galton’s, while his 
theory of evolution would vanish altogether. It is 


64. An Examination of Wetsmannism. 


therefore necessary to quote some of these con- 
cessions, if only to justify ourselves in subsequently 
ignoring them. I will give one instance of each ; 
but it is necessary to preface the illustrations with 
a few words to mark emphatically three very 
distinct cases of congenital variation—leaving aside 
for the present the question whether or not they all 
occur in fact, as they are held to do by one or other 
of the theories of heredity. 

1. The case where impoverished nutrition of the 
body has the effect of simply starving its germinal 
material. This isnot a case where either the continuity 
or the stability of such material is affected. Its full 
efficiency as “formative material’? may indeed be 
thus deteriorated to any extent, so that the progeny 
may be to any extent puny or malformed; but this 
will not necessarily cause any such re-shuffling of its 
“molecules” as will thereafter result in a permanent 
phylogenetic change. At most it will affect only the 
immediate offspring of poorly nourished parents; and 
natural selection will always be ready to eliminate 
such inefhcient individuals. This case I will always 
hereafter call the case of zatrztive congenital changes. 

2. The case where germinal material is influenced 
by causes which do effect a re-shuffling of its “ mole- 
cules,’ so that a permanent phylogenetic change 
does result. Observe, in this case, it does not signify 
whether the causes arise from external conditions of 
life, from any action of the soma on its own germinal 
material, or from so-called “spontaneous” changes 
on the part of such material itself. But the one 
cause which has not been concerned in producing an 
hereditary modification of this class is the mixture 


Wersmanun’s theory of Fleredity (1891). 65 


of “germ-plasms” in an act of sexual union. In 
hereafter speaking of this case I will follow Weismann’s 
terminology, and call congenital changes thus produced 
specialized congenital changes. 

3. Lastly, we have the case of the Lamarckian 
factors. This precisely resembles case 2, save that 
the congenital changes produced are still more 
“specialized.” For while in the preceding case 
the re-shuffling before mentioned may have produced 
a congenital change of any kind, in the present case 
the congenital change produced must be of one 
particular kind—viz., a reproduction by heredity of 
the very same modification which occurred in the 
parents. ‘‘The fathers have eaten sour grapes, and 
the children’s teeth are set on edge.” This would be 
an extreme example of “use-inheritance,” and so of 
case 3. But if the fathers had eaten sour grapes, 
and the children, instead of having their teeth set 
on edge, were to be born with a wryneck or a squint, 
then we should have a good example of case 2. In 
order, then, to mark the important distinction between 
these two cases, I will hereafter call the highly 
specialized changes due to the Lamarckian factors— 
supposing such changes to be possible—representative 
congenital changes. 

These several distinctions being understood, I will 
proceed to furnish the two quotations from Weismann, 
which are respectively illustrative of his concessions 
touching his two fundamental postulates, as previously 
explained. 


We may fairly attribute to the adult organism influences 
which determine the phyletic development of its descendants. 
For the germ-cells are contained in the organism, and the 

F 


66 An Examination of Wetsmannism. 


external influences which affect them are intimately connected 
with the state of the organism in which they lie hid. If it be 
well nourished, the germ-cells will have abundant nutriment ; 
and, conversely, if it be weak and sickly, the germ-cells will be 
arrested in their growth. It is even possible that the effects of 
these influences may be more specialized; that is to say, they 
may act only upon certain parts of the germ-cells. But this is 
indeed very different from believing that the changes of the 
organism which result from external stimuli can be transmitted 
to the germ-cells, and will re-develop in the next generation at 
the same time as that at which they arose in the parent, and in 
the same part of the organism’. 


It will be perceived that Weismann himself here 
very clearly draws all the distinctions between cases 
I, 2, andieg.Jas above; explained. aa. nercioremtin 
becomes the more remarkable that he should not 
have perceived how radically inconsistent it is in him 
thus to entertain as “ possible” congenital variations 
belonging to the case 2. For, as we have now so 
fully seen, the theory of germ-plasm (as distinguished 
from that of stirp) cannot entertain the possibility of 
an hereditary and specialized change of azy kind as 
thus produced by external conditions of life: should 
such a possibility be entertained, there must obviously 
be an end to the absolute stability of germ-plasm, 
and a consequent collapse of Weismann’s theory of 
evolution. Either germ-plasm is absolutely stable, 
or else it is but highly stable. If it is absolutely 
stable, individual variations of an hereditary kind can 
occur only as results of sexual admixtures of germ- 
plasm, and Weismann’s theory of evolution is 
established. But if germ-plasm is not absolutely 
stable (no matter in how high a degree it may be so) 

1 Essays, &c., 2nd ed., p. 105. 


Weismann's theory of fleredity (1891). 67 


hereditary individual variations may be produced by 
other causes, and Weismann’s theory of evolution 
collapses. Therefore, if we are to examine his 
_theory of evolution, we can do so only by ignoring 
such a passage as the one just quoted, which sur- 
renders the postulate of the adsolute stability of germ- 
plasm. 

Again, if we are to examine Weismann’s theory of 
heredity, we must similarly ignore such a passage as 
the following, where he represents that he is similarly 
prepared to surrender his still more fundamental 
postulate of the perpetual continuity of germ-plasm. 

After remarking that some of his own experiments 
on the climatic varieties of certain butterflies raise 
such difficulties against his whole theory of heredity 
that even now he “cannot explain the facts otherwise 
than by supposing the passive acquisition of characters 
produced by the direct influence of climate,” he goes 
on to remark more generally—‘ We cannot exclude 
the possibility of such a transmission occasionally 
occurring, for, even if the greater part of the effects 
must be attributed to natural selection, there might 
be a smaller part in certain cases which depends 
on this exceptional factor!”—i.e., the Lamarckian 
factor ! 

Now, it must be particularly noted that in this 
passage Weismann is speaking, not as in the previous 
passage, of sepczalized congenital characters, but of 
representative congenital characters. In other words, 
he here entertains the possibility which in the passage 
previously quoted he very properly rejects—namely, 
“that changes of the organism which result from 





1 Essays, &c., 2nd ed., p. 100. 
F 2 


68 An Examination of Wersmanursm. 


external stimuli can be transmitted to the germ-cells, 
and will re-develop in the next generation at the same 
time as that at which they arose in the parent, and in 
the same part of the organism.” But it is evident that 
if the theory of germ-plasm is undermined by the 
concession made in the passage thus previously 
quoted, in the passage last quoted a match is put 
to the fuse. It does not signify whether the particular 
case of the butterflies in question will ever admit of 
any other explanation more in accordance with the 
theory of germ-plasm: the point is that in zo case 
can this theory entertain the possibility of causes 
other than admixtures of germ-plasm in sexual 
unions producing hereditary changes, (A) of any 
kind, (B) still less of a specialized kind, and (C) least 
of all of a representative kind. For the distinguishing 
essence of this theory is, that germ-plasm must always 
have moved, so to speak, in a closed orbit of its own: 
its “sphere” must have been perpetually distinct 
from those of whatever other “plasms” there may 
be in the constellations of living things. So that, in 
such passages as those just quoted, Weismann is not 
only destroying the very foundations of his general 
theory of evolution, but at the same time he is 
identifying his more special theory of heredity with 
those which had been already published by _ his 
predecessors, and more particularly by Galton. 
Now, it is not Galton’s theory that we are con- 
sidering; and therefore we must hereafter ignore 
those fundamental admissions, whereby Weismann 
every now and again appears ready to relinquish all 
that is most distinctive of, or original in, his own 
elaborate system of theories. 


Wersmann's theory of Heredity (189i). 69 


It is, indeed, impossible not to admire the candour 
of these admissions, or to avoid recognizing the truly 
scientific spirit which they betoken. But, at the same 
time, one is led to doubt whether in making them 
Professor Weismann has sufficiently considered their 
full import. He appears to deem it of comparatively 
little importance whether or not acquired characters 
can sometimes and in some degrees influence the 
hereditary qualities of germ-plasm, provided he can 
show that much the larger part of the phenomena of 
heredity must be ascribed to the continuity of germ- 
plasm. In other words, he seems to think that it 
matters but little whether in the course of organic 
evolution the Lamarckian factors have played but 
a very subordinate part, or whether they have not 
played any part at all. Moreover, I have heard one 
or two prominent followers of Weismann give public 
expression to the same opinion. Therefore I must 
repeat that it makes a literally immeasurable difference 
whether we suppose, with Galton, that the Lamarckian 
factors may sometimes and in some degrees assert 
themselves, or whether we suppose, with the great 
bulk of Weismann’s writings and in accordance with 
the logical requirements of 4zs theory, that they can 
never possibly occur in any degree. The distinctive 
postulate of his theory of heredity, and one of the 
two fundamental doctrines on which he founds his 
further theory of evolution, is, that the physiology of 
sexual reproduction cannot admit of any inversion of 
the relations between “germ-plasm ” and “ somatic idio- 
plasm!’ This is a perfectly intelligible postulate, but 
it is not one with which we may play fast and loose. 


1 See for example, Zssays, p. 229. 


70 An Examination of Wetsmannism. 


Either there is such a physiological mechanism as it 
announces, in which case the relations in question can 
never be inverted “ occasionally,’ any more than rags 
may “occasionally” help to construct the mill which 
is to form them into paper ;—or else there is no such 
mechanism, in which case we may have to do with 
geminules, physiological units, stirp, micellae, pangenes, 
plastidules, or any of the other hypothetical “ carriers 
of heredity ” to which our predilections may happen 
to incline; but the one substance with which we 
certainly have not to do is germ-plasm}. 


After these tedious but necessary preambles, we 
may now proceed to examine Professor Weismann’s 
postulate as to the perpetual continuity of germ-plasm, 
with its superstructure in his theory of heredity— 
reserving for the next chapter our examination of his 
further postulate touching the absolute stability of 
germ-plasm, with its superstructure in his theory of 
evolution. 

The evidence which Weismann has presented in 
favour of his fundamental postulate of the perpetual 
continuity of germ-plasm may be conveniently dealt 


' On previous occasions, when inconsistencies have been brought to 
the notice of Professor Weismann by his critics, he has complained that 
sufficient allowance was not made for the fact of his having published 
his sundry essays at different times. This, of course, is a satisfactory 
answer in cases where criticism refers to a growing theory, the later 
additions to which supersede certain parts of the earlier construction. 
But clearly the answer is not available in cases where one set of 
statements, touching fundamental principles of the theory, are directly 
opposed to others. A logical contradiction is not affected by dates 
of publication, and where the contradictory statements have reference 
to the vital essence of a theory, it is equally impossible for the theory 
to comprise them whether they be presented simultaneously or suc- 
cessively. 


Wetsmann's theory of Heredity (1891). 71 


with under two heads—namely, indirect evidence as 
derived from general reasoning, and direct evidence 
derived from particular facts. 

The general reasoning is directed to show, (1) that 
there is no evidence of the transmission of acquired 
characters; (2) that the theory of pangenesis is 
“inconceivable”; and, (3) that the alternative theory 
of germ-plasm is amply conceivable. Now, to the 
best of my judgement, not one of these propositions is 
borne out by the general reasoning in question. But 
as the latter is almost entirely of an @ przorz character, 
and also of a somewhat abstruse construction, I think 
the patience of any ordinary reader will be saved by 
relegating this part of our subject to an Appendix. 
Therefore, remarking only that any one who cares to 
look at Appendix I ought, in my opinion, to perceive 
that there is no real evidence against the transmission 
of acquired characters to be derived from Weismann’s 
general reasoning in this connexion, I will at once 
proceed to consider the evidence which he has 
adduced in the way of particular facts. 


In the first place, as one result of his brilliant 
researches on the H/ydromcdusae, he has found that 
the generative cells occur only in certain localized 
situations, which, however, vary greatly in different 
species, though they are always constant for the same 
species. He has also found that the varying situations 
in different species of the localized or generative areas 
correspond, place for place, with successive stages in 
a process of gradual transposition which has occurred 
in the phylogeny of the Hydromedusae. Lastly, he 
has found that in each ontogeny these successive 


72 An Examination of Wetsmannism. 


stages of transposition are repeated, with the result 
that during the individual lifetime of one of these 
animals the germ-cells migrate through the body, from 
what used to be their ancestral situation to what is 
now the normal situation for that particular species. 
Such being the facts, Weismann argues from them 
that the germ-cells of the ydromedusae are thus 
proved to present properties of a peculiar kind, which 
cannot be supplied by any of the other cells of the 
organism ; for, if they could, whence the necessity for 
this migration of these particular cells? Of course 
it follows that these peculiar properties must depend 
on the presence of some peculiar substance, and that 
this is none other than the ‘‘ germ-plasm,’ which here 
exhibits a demonstrable “ continuity” throughout the 
entire phylogeny of these unquestionably very ancient 
Metazoa. 

The second line of direct evidence in favour of the 
continuity of germ-plasm which Weismann has ad- 
duced is, that in the case of some invertebrated animals 
the sexual apparatus is demonstrably separated as 
reproductive cells (or cells which afterwards give rise 
to the reproductive glands) at a very early period of 
ontogeny—so early indeed, in certain cases, that this 
separation constitutes actually the first stage in the 
process of ontogeny. ‘Therefore, it is argued, we may 
regard it as antecedently improbable that the after-life 
of the individual can in any way affect the congenital 
endowments of its ova, seeing that the ova have been 
thus from the first anatomically isolated from all the 
other tissues of the organism. 

The third and only other line of direct evidence is, 
that organisms which have been produced partheno- 


Wetsmann's theory of Heredity (1891). 73 


genetically, or without admixture of germ-plasms in 
any previous act of sexual fertilization, do not exhibit 
congenital variations. 

Taking, then, these three lines of verification separ- 
ately, none of them need detain us long. For although 
the fact of the migration of germ-cells becomes one of 
great interest in relation to Weismann’s theory after 
the theory has been accepted, the fact in itself does not 
furnish any evidence in support of the theory. In 
the first place, it tends equally well to support Galton’s 
theory of stirp; and therefore does not lend any 
special countenance to the theory of germ-plasm—or 
the theory that there cannot now be, and never can 
have been, any communication at all between the 
plasm of the germ and that of the soma. In the 
second place, the fact of such migration is not incom- 
patible even with the theory of pangenesis, or the 
theory which supposes such a communication to be 
extremely intimate. There may be many other 
reasons for this migration of germ-cells besides the 
one which Weismann’s theory supposes. For example, 
the principle of physiological economy may very 
well have determined that it is better to continue for 
reproductive purposes the use of cells which have 
already been specialized and set apart for the execu- 
tion of those purposes, than to discard these cells 
and transform others into a kind fitted to replace 
them. Even the theory of pangenesis requires to 
assume a very high degree of specialization on the 
part of germ-cells; and as it is the fact of such 
specialization alone which is proved by Weismann’s 
observations, I do not see that it constitutes any 
criterion between his theory of heredity and that of 


74 An Examination of Wetsmannism. 


Darwin—-still less, of course, between his theory and 
that of Galton. Lastly, in this connexion we ought 
to remember that the Hydromedusae are organ- 
isms in which the specialization in question happens 
to be least, as is shown by the fact that entire indi- 
viduals admit of being reproduced from fragments of 
somatic-tissues; so that these are organisms where 
we would least expect to meet with the migration 
of germ-cells, were the purpose of such migration 
that which Weismann suggests. This line of evidence 
therefore seems valueless. 

Nor does it appear to me that the second line of 
evidence is of any more value. In the first place, 
there is no shadow of a reason for supposing that an 
apparently anatomical isolation of germ-cells neces- 
sarily entails a physiological isolation as regards 
their special function—all ‘“ physiological analogy,’ 
indeed, being opposed to such a view, as is shown 
in Appendix I. In the second place, there is no 
proof of any anatomical isolation, as we may like- 
wise see in that Appendix. In the third place, the 
fact relied upon to indicate such an isolation—viz., 
the early formation of germ-cells—is not a fact of any 
general occurrence. On the contrary, it obtains only 
in a comparatively small number of animals, while it 
does not obtain in any plants. In the Vertebrates, 
for example, the reproductive cells are not dif- 
ferentiated from the somatic cells till after the em- 
bryo has been fully formed; while in plants their 
development constitutes the very last stage of onto- 
geny. In the fourth place, the argument, even for 
what it is worth, is purely deductive ; and deductive 
reasoning in such a case as this—where the phonemena 


Weismann's theory of Heredity (1891). 75 


are enormously complex and our ignorance unusually 
profound—is always precarious. Lastly, in the fifth 
place, Weismann has now himself abandoned this 
argument. For in one of his later essays he says :-— 


Those instances of early separation of sexual from somatic 
cells, upon which I have often insisted as indicating the con- 
tinuity of the germ-plasm, do not now appear to be of such 
conclusive importance as at the time when we were not sure 
about the localization of the plasm in the nuclei. In the great 
majority of cases the germ-cells are not separated at the 
beginning of embryonic development, but only in some of the 
later stages. ... It therefore follows that cases of early separa- 
tion of the germ-cells afford no proof of a direct persistence of 
the parent germ-cells in those of the offspring. 


The last line of direct evidence, or that derived 
from the alleged non-variability of parthenogenetic 
organisms, is, as Professor Vines has shown, opposed 
to fact. Therefore, in his later writings, Weismann 
has abandoned this line of evidence also. 

Upon the whole, then, we must conclude with regard 
to the fundamental postulate of perpetual continuity, 
that there is actually no evidence of a direct kind in 
its favour. And, as Weismann’s arguments of an 
indirect kind are dealt with in Appendix I, it remains 
only to state such evidence per contra as, to the best 
of my judgement, appears valid. 


The fundamental proposition which we have been 
considering, and to the further consideration of which 
we have now to proceed, is, in effect, that germ-plasm 
differs from stirp in having been ferpetual/y restricted 
to a “sphere”’ of its own, “szzce the first origin of 
life.” Criticism, therefore, must be directed to show 
that the “sphere” in question has not been proved 


76 An Examination of Weismanntsm. 


so entirely independent as this fundamental proposition 
sets forth; but that, on the contrary, there appears 
to be a certain amount of reciprocal action between 
this sphere and that of the somatic-tissues—even 
though we may agree (as I myself agree) with Galton 
in holding that the degree of such _ reciprocal 
action is neither so intimate nor so constant as it 
was held to be by Darwin. This, indeed, is the 
direction which the course of our criticism has taken 
already. For it has just been shown that Weismann 
has failed to adduce any facts (preceding text) or 
considerations (Appendix I) in support of his fun- 
damental proposition as above stated, save such as 
proceed on a prior acceptance of the proposition 
itself. The facts and considerations which he has 
adduced are therefore useless as evidence in support 
of this proposition, although they would admit of 
being explained by it supposing it to have been 
already substantiated by any facts or considerations of 
an independent kind. Which is merely another way of 
saying, as already said, that there is no evidence in 
favour of the proposition. | 

But Iam now about to argue that there zs evidence 
against the proposition. For I am about to argue, 
not only as heretofore that for anything Weismann has 
shown to the contrary there may be a certain amount 
of reciprocal action between the sphere of germinal- 
substance and the sphere of body-substance ; but that, 
as a matter of fact, there zs a certain amount of such 
reciprocal action. 

Without laying undue stress on the intimate 
“correlation” that subsists between the reproductive 
organs and all other parts of the organism, I never- 


Wetsmann's theory of Heredity (1891). 77 


theless think that the fact ought here to be noted. 
For the changes which occur at puberty and after the 
reproductive functions have ceased, as well as those 
which may be artificially produced by castration, 
&c., prove at any rate some extremely important 
association between the soma as a whole and its 
reproductive apparatus as a whole. No doubt it may 
properly enough be answered that this proof does not 
extend to the vital point of showing the association 
to be between the soma as a whole, and that particular 
part of the reproductive apparatus in which the 
“carriers of heredity” reside—namely, the ova and 
spermatozoa ; and, therefore, that the facts in question 
may be due only to some changed conditions of 
nutrition on the part of the somatic-tissues which 
these alterations on the part of the reproductive glands 
entail. On this account we must fully allow that the 
facts in question are not in themselves of any con- 
clusive weight ; but I think they are worth mentioning, 
because they certainly seem to countenance the theory 
which supposes some reciprocal influence as exercised 
by the germinal elements on the somatic-tissues and 
vice versa, rather than they do the theory which sup- 
poses the germinal elements and the somatic-tissues 
to have always occupied totally different “spheres.” 
Here, however, is a stronger class of facts. It has 
not unfrequently been observed, at any rate in mam- 
mals, that when a female has borne progeny to 
a male of one variety, and subsequently bears progeny 
to a male of another variety, the younger progeny 
presents a more or less unmistakable resemblance to 
the father of the older one. Now, this is a fact to 
which Weismann has nowhere alluded ; and therefore 


78 An Examination of Wersmannism. 


I do not know how he would meet it. But, as far as 
I can see, it can be explained only in one or other of 
two ways. Either there must be some action of the 
spermatic element on the hitherto unripe ovum, or else 
this element must exercise some influence on the so- 
matic-tissues of the female, which in their turn act upon 
the ovum!. Now, I do not deny that the first of these 
possibilities might be reconcilable with the hypothesis 
of an absolute continuity of germ-plasm; for it is 
conceivable that the life of germ-plasm is not co- 
terminous with that of the spermatozoa which convey | 
it, and hence that, if the carriers of heredity, after the 
disintegration of their containing spermatozoa, should 
ever penetrate an unripe ovum, the germ-plasm thus 
introduced might remain dormant in the ovum until the 
latter becomes mature, and is then fertilized by another 
sire. In this way it is conceivable that the hitherto 
dormant germ-plasm of the previous sire might exercise 
some influence on the progeny of a subsequent one. 
But it seems clear that the second of the two possi- 
bilities above named could not be thus brought within 
the hypothesis of an absolute continuity of germ- 
plasm. Therefore it seems that the school of Weis- 
mann must adopt the first, to the exclusion of the 
second. Unfortunately for them, however, there is 
another (and clearly analogous) fact, which goes to 
exclude the first possibility, and most definitely to 
substantiate the second. For, in the case of plants, 
where there can be no second progeny borne by the 


1 The possibility of any spermatozoa of the first impregnation 
surviving to take part in the second is excluded by the fact that the 
phenomenon occurs in mammals, and, apparently, may extend over tw¢ 
or three litters. 


Wersmann's theory of Feredity (1891). 79 


same “ ovary,” but where we happen to be able to see 
that a marked effect is sometimes produced on the 
somatic-tissues of the mother by the pollen of the 
father, there can be no question as to the male element 
being able to exercise a direct influence on the soma 
of the female. Consequently, whatever we may think 
with regard to the case of animals, the facts with regard 
to plants are in themselves enough to sustain the only 
position with which we are concerned—viz., that the 
male element is capable of directly modifying the 
female soma. 

The facts with regard to plants are these. When 
one variety fertilizes the ovules of another, not 
unfrequently the influence extends beyond the ovules 
to the ovarium, and even to the calyx and flower- 
stalk, of the mother plant. This influence, which 
may affect the shape, size, colour, and texture of the 
somatic-tissues of the mother, bas been observed in a 
large number of plants belonging to many different 
orders. The details of the matter have already been 
dealt with by Darwin, in the eleventh chapter of his 
work on Variation, &c.; and this is what he says. 
The italics are mine. | 


The proofs of the action of foreign pollen on the mother-plant 
have been given in considerable detail, because this action is of 
the highest theoretical importance, and because it is in itself 
a remarkable and apparently anomalous circumstance. That it 
is remarkable under a physiological point of view is clear, for 
the male element not only affects, in accordance with its proper 
function, the germ, but at the same time various parts of the 
‘mother-plant, 77 the same manner as tt affects the same parts in 
the seminal offspring from the same two parents. We thus 
learn that an ovule is not indispensable for the reception of the 
influence of the male element. 


80 An Examination of Wetsmanunism. 


Darwin then proceeds to show that this direct action 
of the male element on the somatic tissues of another 
organism is not so rare or anomalous as it at first 
sight appears; for in the case of not a few flowers it 
comes into play as a needful preliminary to fertiliza- 
tion. Thus, for instance :— 


Gartner gradually increased the number of pollen grains 
until he succeeded in fertilizing a Malva, and has proved that 
many grains are first expended in the development, or, as he 
expresses it, in the satiation, of the pistil and ovarium. Again, 
when one plant is fertilized by a widely distinct species, it often 
happens that the ovarium is fully and quickly developed 
without any seeds being formed ; or the coats of the seeds are 
formed without any embryo being developed therein, 


So much, then, in proof of the direct action of 
the male element on the somatic-tissues of another 
organism. It remains to show that a similar action 
may be exercised by this element on the somatic- 
tissues of its own organism. This has been proved by 
Hildebrand, who found “that in the normal fertiliza- 
tion of several Orchideae, the action of the plant’s 
own pollen is necessary for the development of the 
ovarium; and that this development takes place not 
only long before the pollen tubes have reached the 
ovules, but even before the placentae and ovules have 
been formed”; so that with these orchids the pollen 
acts directly on their own ovaria, as a preliminary to 
the formation of the ovules which are subsequently 
to be fertilized. 

It is to be regretted that Professor Weismann 
has not given us his opinion upon this whole class 
of facts, for assuredly they appear directly to con- 
tradict his theory. The theory is, “that the germ- 


Wetsmann's theory of fleredity (1891). 81 


plasm and the somato-plasm have always occupied 
different spheres”: the fact is, that the germ-plasm 
may directly act upon the somato-plasm, both within 
and beyond the limits of the same organism. 


Hitherto we have been considering certain very 
definite facts, which seem to prove that the germinal 
elements are able directly to affect the somatic-tissues. 
We have next to consider such facts as seem to prove 
the opposite side of a reciprocal relationship—viz., 
that the somatic-tissues are able directly to affect 
the germinal elements. 

And here there are two distinct lines of evidence 
to be distinguished. 

Firstly, in certain cases—exceptional it is true, but 
this does not signify —somatic-tissues have been found 
capable of modifying the hereditary endowments of 
germinal elements by means of simple grafting. This 
line of evidence has also been disregarded both by 
Weismann and his followers; but it is nevertheless an 
important one to consider. For, if it be the case 
that the somatic-tissues of an organism A, by being 
merely grafted on those of organism B, can so affect 
the germinal elements of B as to cause their offspring 
to resemble A—or, contrariwise, if the somatic-tissues 
of A can thus act on B—then, although it may not 
be properly said that any “acquired characters” have 
been transmitted from A to the progeny of B, (or 
vice versa,) such an a-sexual transmission of alien 
characters, in its relation to the theory of germ-plasm, 
is scarcely less awkward than are certain facts which 
they appear to prove. 

Secondly, that acquired characters may be trans- 

G 


82 An Lxamination of Weismannism. 


mitted to progeny by the more ordinary methods of 
sexual propagation (Lamarckian factors). This second 
line of evidence will be fully and independently dealt 
with in future chapters, specially devoted to the 
subject. Therefore we have here to consider only the 
first. 

Now, the force of this first line of evidence will 
become apparent, if we reflect that the only way 
in which the facts can be met by Weismann’s theory, 
would be by supposing that the somatic germ-plasms 
which are respectively diffused through the cellular 
tissues of the scion and the graft become mixed in 
some such way as they might have been, had the 
hybrid been due to seminal propagation instead of to 
simple grafting. But against this, the only interpre- 
tation of the facts which is open to the theory, there 
lies the following objection, which to me appears 
insuperable. 

Where sexual cells are concerned there is always 
a definite arrangement to secure penetration of the 
one by the other, and we can see the necessity for 
such an arrangement in order to effect an admixture of 
their nuclear contents, where alone germ-plasm is 
supposed by Weismann’s theory to reside. But in 
tissue-cells, which have not been thus specialized, it 
would be difficult to believe that nuclear contents can 
admit of being intimately fused by a mere apposition 
of cell-walls. For not only are the nuclear contents of 
any two such cells thus separated from one another 
by two cell-walls and two masses of “cytoplasm” ; 
but it is not enough to suppose that in order to 
produce a graft-hybrid only two of these somatic-cells 
need mix their nuclear contents as we know is all 


Wetsmann's theory of Hereaity (1891). 83 


that is required in order to produce a seminal hybrid 
by means of sexual cells. On the contrary, in the 
former case most, if not all, the somatic-cells which 
are brought into apposition by the graft must be 
supposed thus to mix their nuclear contents at the 
plane of the graft; for otherwise the hybrid would not 
afterwards present equally the characters of stock and 
scion. Now, there may be hundreds of thousands of 
such cells, and therefore it seems impossible that the 
facts of graft-hybridization can be reconciled with the 
theory of germ-plasms!. 

The third line of evidence against this theory— 
i.e., the evidence in favour of the transmission of 
acquired characters—is to constitute the subject- 
matter of future chapters. Therefore it will here be 
sufficient to adduce only one fact of this kind. And 
I select it because it is one that has been dealt with by 
Weismann himself. In one of his more recent state- 
ments he says :-— 


The distinguished botanist De Vries has proved that certain 
constituents of the cell body—e.g., the chromatophores of 
Algae—pass directly from the maternal ovum to the daughter 
organism, while the male germ-cells generally contain no 
chromatophores. Here it appears possible that a transmission 
of somatogenetic variation has occurred ”. 


Now although, as Weismann goes on to observe, 


1 Possibly the school of Weismann may simply refuse to accept the 
facts, which are confessedly rare, and, in many of the cases alleged, 
dubious. In other cases, however, the evidence is sufficient to have 
satisfied the cautious judgement of Darwin, who has discussed it in 
detail. Therefore, even if the Neo-Darwinians repudiate this evidence, 
at least they ought to state that such is the position which they 
adopt. 

* Nature, Feb. Oth, 1890. 

G 2 


84. An Examination of Wersmannism. 


“in these lower plants, the separation between somatic 
and reproductive cells is slight,” in the facts'to which 
he alludes we appear to have good evidence of an 
influence exercised by somatic cells upon the germinal 
contents of reproductive cells. And ifsuch an influence 
is capable of being exercised in the case of “these 
lower plants,” it follows that there is no such absolute 
separation between somatic tissues and germ-plasm as 
Weismann’s theory requires. Moreover it follows 
that, if the essential distinction between germ-plasm 
and somato-plasm (or “somatic idioplasm”) is thus 
violated at the very foundation of the multicellular 
organisms, there ceases to be any @ przorz reason for 
drawing arbitrary limits, either as to the level of organ- 
ization at which such ‘transmission of somatogenetic 
variation has occurred,” or as to the degree of detail 
into which it may extend. Both these matters then 
stand to be tested by observation ; and the burden of 
proof lies with the school of Weismann to show at 
what level of organization, and at what degree of 
representation, somatogenetic changes cease to repro- 
duce themselves by heredity. | 

Passing on, then, to higher levels of organization, 
and therefore to higher degrees of representation, 
I shall endeavour to show that this burden of proof 
cannot be discharged. For I shall endeavour to 
show, not merely, as just shown, that there ceases 
to be any @ priorz reason for drawing arbitrary 
limits with respect. either to levels of organization 
or to degrees of representation, but that, as a matter 
of fact, there are no such limits as the passage above 
quoted assigns. On the contrary, I believe there 
is as good evidence to prove the not unfrequent 


Wetsmann’s theory of Heredity (1891). 85 


transmission of acquired (“ somatogenetic ”) characters 
among the higher plants—and even among the higher 
animals—as there is of the occurrence of this phe- 
nomenon in the case of the Alga just mentioned. But 
in order to do this evidence justice, I shall have to 
take a new point of departure and consider as a 
separate question the transmissibility of acquired char- 
acters. Meanwhile, and as far as Weismann’s theory 
of heredity is concerned, it is enough to have shown,— 
if I have been successful in doing so,—that not only 
is there no evidence to sustain his fundamental postu- 
late touching the material of heredity having always 
occupied a separate “sphere” of its own “since the 
first origin of life’; but that there is good evidence 
to prove the contrary. For whether or not the re- 
ciprocal action of “somato-plasm” and “germ-plasm” 
can ever proceed to the extent of causing acquired 
characters to be inherited (so as to produce “ repre- 
sentative congenital changes”), all that is distinctive 
in this theory must be regarded as barren speculation, 
unless it can be shown that the foregoing facts have 
failed to prove such a reciprocal action as ever 
occurring in any lower degree (so as to produce 
“specialized congenital changes ”). 


GHAR ARE Reaiy 


EXAMINATION OF WEISMANN’S THEORY 
OF EVOLUTION (1891). 


HAVING now considered germ-plasm as perpetually 
continuous, we have next to regard it as unalter- 
ably stable. 

First, let it be noted that these two fundamental 
and distinctive postulates of the whole Weismannian 
system are so intimately connected as to be in large 
measure mutually dependent. For, on the one 
hand, if germ-plasm has not been perpetually con- 
tinuous since the first origin of life, it cannot have 
been absolutely stable “since the first origin of sexual 
propagation”: every time that its hereditary characters 
are modified by its containing soma (whether or 
not representatively so), its stability has been so 
far upset. On the other hand, if germ-plasm has 
not been absolutely stable, it cannot have been per- 
petually continuous “since the first origin of life.” 
As often as its stability has been upset, its “mo- 
lecular structure” has been modified by causes ad 
extra, as distinguished from mixtures of germ-plasms 
in sexual unions. ‘Therefore, it can no longer have 
been continuous in the sense of having borne an 
ineffaceable record of all congenital variations, due ¢o 
sexual unions, throughout the entire phylogeny of 


Weismann's theory of Evolution (1891). 87 


the Metaphyta and Metazoa. At most it can have 
been continuous only in the attenuated sense, that 
however much and however often its hereditary 
characters may have been modified by somatic 
changes on the one hand or by changes in the 
external conditions of life on the other, they can 
never have been thus modified vepresentatively, as 
supposed by the theory of pangenesis. 

From which it follows that, while examining in 
our last chapter Weismann’s doctrine of the per- 
petual continuity of germ-plasm, we have been 
indirectly examining also his companion doctrine of 
the unalterable stability of germ-plasm. Neverthe- 
less, for the sake of doing justice to both these 
doctrines, I have thought it desirable to examine 
each on its own merits, without prejudice arising 
from our criticism of the other. To such a separate 
and independent examination of the doctrine of 
unalterable stability we will, therefore, now proceed. 


As we have already and repeatedly seen, this 
doctrine of the unalterable or absolute stability of 
germ-plasm “since the first origin of sexual propaga- 
tion” is a logically essential part of Weismann’s 
theory of evolution, or of his system of hypotheses 
considered as a whole. It is so because upon this 
doctrine depends his reference of individual variations 
in the Metazoa to an ultimate origin in the Protozoa, 
the significance of sexual reproduction in the theory 
of natural selection, &c., &c. Therefore this doctrine 
of the absolute stability of germ-plasm is enunciated 
by Weismann, not merely for the purpose of meeting 
any one class of facts, such as those of atavism 


88 Ax Examination of Wetsmannism., 


persistence of rudimentary organs, &c. The doctrine 
is enunciated for the purpose of constituting one of 
the foundation-stones of his general theory of evolu- 
tion. We have now to consider how far the quality 
of this stone renders it trustworthy as a basis to build 
upon. 

In the first place, we can scarcely fail to perceive 
that this doctrine of the absolute stability of germ- 
plasm is not only gratuitous, but intrinsically impro- 
bable. That the most complex material in nature 
should likewise be the most stable is opposed 
to all the analogies of nature, and therefore to 
all the probabilities of the case. 

Again, the germ-plasm, as it originally occurred 
(and still exists) in unicellular organisms, is supposed 
to be exactly the same zd of material as now 
occurs in the germ-cells of multicellular organisms. 
Yet the very same theory which supposes so 
absolute a stability on the part of germ-plasm 
when located in germ-cells (or diffused through 
somatic-cells), likewise supposes so high a degree of 
variability on the part of germ-plasm when not thus 
located, as to represent that all individual variations 
which have ever taken place in the unicellular 
organisms—and all the innumerable species of such 
organisms which have arisen therefrom—have been 
due to the direct action of external conditions of life ; 
or, in other words, to the zzstability of germ-plasm. 
The very same substance which at one time and in one 
place is supposed to be so absolutely unchangeable, 
at another time and in another place is supposed to 
be highly susceptible of change. 

Lastly—and this is, perhaps, the most curious part 


Wersmann’s theory of Evolution (1891). 89 


of the whole matter—the place where germ-plasm is 
supposed to be unchangeable is not the place where 
it is most likely to be so, but the place where it is 
least likely. For germ-plasm as it occurs in the germ- 
cells of multicellular organisms must have a constitu- 
tion greatly more complex even than that which it has 
in unicellular organisms—seeing that in the former 
case, and by hypothesis, it bears a living record of the 
whole phylogeny of the Metaphyta and Metazoa in 
all their innumerable branchings. And not only so, 
but when germ-plasm occurs in germ-cells it becomes 
exposed to much greater vicissitudes : its environment 
has become vastly more complex, as well as greatly 
more liable to change with the changing conditions of 
life of the many mutable species in which it resides, 
and on the individual somas of which it now depends 
for itsnourishment. So that, altogether, we have here 
on merely @ priorz grounds about as strong a case 
against this doctrine of absolute stability as it is well 
conceivable that on merely @ priorz grounds a case 
can be. 

Turning next to arguments a posteriorz, let us begin 
by considering those which Weismann has adduced in 
support of the doctrine. 

First, he alleges that there is a total absence of 
variability on the part of all organisms which have 
been produced parthenogenetically, or from unfer- 
tilized ova. We may look in vain, he says, for any 
individual differences on the part of any multi- 
cellular organisms, which have been brought into ex- 
istence independently of the blending of germ-plasms 
in a previous act of sexual union. Now, unques- 
tionably, if this statement could be corroborated by 


90 An Examination of Wetsmannism. 


sufficiently extensive observation, the fact would 
become one of immense significance-—so much so, 
indeed, that of itself it would go far to neutralize all 
antecedent objections, and to verify his theory as to 
sexual propagation being the sole cause of congenital 
variation. But seeing that the alleged fact stands so 
entirely out of analogy with the phenomena of bud- 
variation (which will be alluded to later on), it is 
highly improbable, even on antecedent grounds; while 
Professor Vines has refuted the statement on grounds 
of actual fact. Thus, speaking of the Baszdiomycetes, 
he says— 


These Fungi are not only entirely a-sexual, but it would appear 
that they have been evolved in a purely a-sexual manner from 
a-sexual ascomycetous or ecidiomycetous ancestors. The 
Basidiomycetes, in fact, afford an example of a vast family of 
plants, of the most varied form and habit, including hundreds 
of genera and species, in which, so far as minute and long- 
continued investigation has shown, there is not, and probably 
never has been, any trace of a sexual process *. 


Here, then, we have actual proof of “hereditary 
individual variations” among a-sexually propagating 
organisms, sufficient in amount to have given origin, 
not merely to “individual differences,” but to in- 
numerable species, and even genera. Consequently 
Weismann allows that the criticism abolishes this line 
of evidence in favour of the absolute stability of germ- 
plasm *. Consquently, also, we must now add, in 
whatever measure the alleged fact would have corro- 
borated the theory had it been proved to be a fact, 
in that measure is the theory discredited by proof that 


1 Nature, vol, xl. p. 626. 
* Jord... vol; xii; p..324. 


Weismann's theory of Evolution (1891). 91 


it is not a fact. For, if the theory were sound, this 
particular fact would certainly have admitted of de- 
monstration: therefore the proof that it is not a fact 
—but the reverse of a fact—amounts at the same time 
to a disproof of the theory |. 

The only other line of evidence to be adduced in 
favour of the absolute stability of germ-plasm is that 
which is furnished by the high antiquity of some specific 
types, by the facts of atavism, and by the persistency 
of vestigial organs. But this line of evidence is as 
futile as the other. Nobody has ever questioned 
that hereditary characters are persistently stable as 
long as they are persistently maintained by natural 
selection ; and this, according to Weismann himself, 
must have been the case with all long-enduring 
species: these, therefore, fail to furnish any evidence 
of the zzherent stability of germ-plasm, which is the 
only point in question. 

Again, as regards the facts of atavism, nobody is 
disputing these facts. What we are disputing is 
whether the degree of inherent stability which they 
unquestionably prove can be rationally regarded as 

In his Zssays (vol. i. p. 282) Weismann says :—‘‘ If it could be shown 
that a purely parthenogenetic species had become transformed into a 
new one, such an observation would prove the existence of some new 
force of transformation other than selective processes, for the new species 
could not have been produced by these latter.” But now it has been 
shown that a purely parthenogenetic species can be transformed into 
a new one, and therefore it seems desirable to note that the observation 
does not so much as tend to prove the existence of some new force 
of transformation other than selective processes. Forthis most singular ° 
statement can only stand on a prior acceptance of Weismann’s own 
assumption, as to amphigony being the only possible cause of individual 
hereditary variation. Only if we have already, and with absolute 
certainty, embraced the whole Weismannian creed, could we consent to 


affirm that “natural selection is an impossibility in a species propagated 
by a-sexual reproduction.” 


92 An Examination of Wetsmanunism. 


such that it may endure, not merely for such a com- 
paratively small number of generations as these facts 
imply, but actually for any number of generations, 
or through the practically infinite series of generations 
that now intervene between the higher metazoa and 
their primeval parentage in the protozoa. Clearly, 
the ratio between these two things is such that no 
arcument derived from the facts of atavism can be 
of any avail for the purposes of this Weismannian 
doctrine. 

Lastly, as regards vestigial organs, the consideration 
that, surprisingly persistent as they unquestionably are, 
nevertheless they do eventually disappear, seems to 
prove that the power of heredity does in time become 
exhausted, even in cases most favourable to its con- 
tinuance. That it should thus become finally ex- 
hausted is no more than Darwin’s theory of perishable 
gemmules, or Gaalton’s theory of a not absolutely 
stable stirp, would expect. But’ the fact is irre- 
concilable with Weismann’s theory of an absolutely 
stable germ-plasm. 

Hence, we can only conclude that there is no 
evidence in favour of the hypothesis that germ-plasm 
has been unalterably stable “since the first origin 
of sexual propagation”; while the suggestion that 
it may have been so is on antecedent grounds im- 
probable, and on inductive grounds untenable. It 
only remains to add that the degree of stability 
has been proved in not a few cases to be less than 
even the theory of gemmules might anticipate. Many 
facts in proof of this statement might be given, but it 
will here suffice to quote one, which I select because 
it has been dealt with by Professor Weismann himself. 


Wetsmann's theory of Evolution (1891). 93 


Professor Hoffmann has published an abstract of 
a research, which consisted in subjecting plants with 
normal flowers to changed conditions of life through 
a series of generations. In course of time, certain well- 
marked variations appeared. Now, in some cases such 
directly-produced variations were transmitted by seed 
from the affected plants; and therefore Weismann 
acknowledges,—“ I have no doubt that the results are, 
at any rate in part, due to the operation of heredity.” 
Hence, whether these results be due to the trans- 
mission of somatogenetic characters (“representative 
changes’), or to the direct action of changed conditions 
of life on the germ-plasm itself (‘specialized changes”), 
it is equally certain that the hereditary characters 
of the plants were congenitally modified to a large 
extent, within (at most) a few generations. In other 
words, it is certain that, if there be such a material as 
germ-plasm, it has been proved in this case to have 
been highly unstable. Therefore, in dealing with 
these and other similar facts, Weismann himself can 
only save his postulate of continuity by surrendering 
for the time being his postulate of stability 1. 

If to this it be replied that Hoffmann’s facts are 
exceptional—that Gartner, Nageli, De Candolle, Peter, 

* What he says is:—‘‘It was only after a greater or less number 
of generations had elapsed that a variable proportion of double flowers 
appeared, sometimes accompanied by changes in the leaves and in the 
colours of the flowers. Zhzs fact admits of only one interpretation :— 
the changed conditions at first produced slight and ineffectual changes 
in the idio-plasm of the individual, which was transmitted to the following 
generation... . . Now, the idio-plasm of the first ontogenetic grade 
(viz., germ-plasm) alone passes from one generation to another, and 
hence it ts clear that the germ-plasm itself must have been gradually 
changed by the condctions of life, until the alteration became suffictent to 


produce changes in the soma, which appeared as visible characters in 
etther flower or leaf.’—Essays, pp. 420-7 ; italics mine. 





94 An Lxamination of Wetsmannism. 


Jordan, and others, did not find individual variations 
produced in plants by changed conditions of life to 
be inherited,—the reply would be irrelevant. It does 
not require to be proved that all variations produced 
by changed conditions of life are inherited. If only 
some—even though it be but an extremely small 
percentage—of such variations are proved to be 
inherited, the many millions of years that separate 
the germ-plasm of to-day from its supposed origin 
in the protozoa, must have furnished opportunities 
enough for the occurrence of such variations to have 
obliterated, and re-obliterated numberless times, any 
aboriginal differences in the germ-plasms of in- 
cipiently sexual organisms. Moreover, it is probable 
that when further experiments shall have been made 
in this direction, Hoffmann’s results will be found 
not so exceptional as they at present appear. 
Mr. Mivart, for example, has mentioned several 
instances!; while there are not’ a few. facts: of 
general knowledge—such as the modifications under- 
gone by certain Crustacea as a direct result of 
increased salinity of the water in which they live— 
that will probably soon be proved to be facts of the 
same order. But here attention must be directed 
to another large body of facts, which are of high 
importance in the present connexion. 

The phenomena of what is called bud-variation in 
plants are phenomena of not infrequent occurrence, 
and they consist in the sudden appearance of a 
peculiarity on the part of a shoot which develops 
from a single bud. When such a peculiarity arises, 
it admits of being propagated, not only by cuttings 

1 Nature, Nov. 14, 1889, p. 41. 


Wetsmann's theory of Evolution (1891). 95 


and by other buds from that shoot, but sometimes 
also by seeds which the flowers of the shoot sub- 
sequently produce—in which case all the laws 
of inheritance that apply to congenital variations 
are found to apply also to bud-variation. Or, as 
Darwin puts it, “there is not any particular in which 
new characters arising by bud-variation can be dis- 


b) 


tinguished from those due to seminal variation” ; 
and, therefore, any theory which deals with the latter 
is bound also to take cognizance of the former. Now, 
as far as I can find, there is only one paragraph in 
which Weismann alludes to bud-variation, and what 
he there says I do not find very easy to understand. 
Therefore I will quote the whole paragraph verbatim. 


I have not hitherto considered budding in relation to my 
theories, but it is obvious that it is to be explained, from my 
point of view, by supposing that the germ-plasm which passes 
on into a budding individual consists not only of the un- 
changed germ-plasm of the first ontogenetic stage, but of this 
substance altered, so far as to correspond with the altered 
structure of the individual which arises from it—viz., the root- 
less shoot which springs from the stem or branches. The 
alteration must be very slight, and perhaps quite insignificant, 
for it is possible that the differences between the secondary 
shoots and the primary plant may depend chiefly on the changed 
conditions of development, which takes place beneath the 
earth in the latter case, and in the tissues of the plant in the 
former. Thus we may imagine that the idio-plasm [? of that 
particular bud], when it develops into a flowering shoot, produces 
at the same time the germ-cells which are found in the latter. 
We thus approach an understanding of Fritz Miiller’s obser- 
vation ; for if the whole shoot which produces the flower arises 
from the same idio-plasm which also forms its germ-cells, we can 
readily understand why the latter should contain the same 
hereditary tendencies which were previously expressed in the 
flower which produced them. The fact that variations may 


96 An Examination of Wetsmanntism. 


occur in a single shoot depends on the changes explained above, 
which occur in the idio-plasm during the course of its growth, 
as a result of the varying proportions in which the ancestral 
idio-plasms may be contained in it’. 

The meaning here appears to be twofold. For 
there are only two ways of explaining the phenomena 
of bud-variation. Either they are due to the influ- 
ence of external conditions acting on the particular 
bud in question, or else they are due to so-called 
“spontaneous” changes taking place within the bud 
itself. Possibly it may be both, but at least it must 
be either. Well, in the above passage, Weismann 
appears to assume that it is both. For at the begin- 
ning of the passage he speaks of the “ germ-plasm of 
the first ontogenetic stage” becoming “altered so 
far as to correspond with the altered structure of the 
individual which arises therefrom,’ and he goes on 
to say that the alteration “may depend chiefly on 
the changed conditions of development ”—that is, as 
I understand, the influence of external conditions. 
But at the end of the paragraph he says that “the 
changes which occur in the idio-plasm during the 
course of its growth” in the sporting bud, are due to 
“the varying proportions in which the ancestral idio- 
plasms may be contained in it.” Thus, I take it, 
Weismann here entertains both explanations of the 
phenomena in question: he appears to regard these 
phenomema as partly due to peculiar admixtures of 
ancestral idio-plasms in the bud itself (or “spon- 
taneous” variation), but partly also to an alteration 
of the germ-plasm by its changed condition of develop- 
ment (or variation caused by external conditions), 


1 Essays, 2nd Ed., pp. 331-2. 


Wersmanun's theory of Evolution (1891). 97 


However, it is but of little consequence whether or 
not this is the meaning which Weismann intends to 
convey. For the point we are coming to is, that, 
whatever he intends to convey, “from the point of 
view ” of the theory of germ-plasm, there is only one 
interpretation possible. It is not open to Weismann 
(as it was to Darwin, or even to Galton,) to entertain 
both the explanations, whether separately or in con- 
junction. For germ-plasm (unlike gemmules, or even 
stirp) must be held always and everywhere wsalterably 
stable: else the whole superstructure of Weismann’s 
theory of evolution falls to the ground. We cannot 
consent to his retaining this theory on the one hand, 
and, on the other, explaining bud-variation by ‘‘ germ- 
plasm of the first ontogenetic stage” becoming 
altered “chiefly by changed conditions of develop- 
ment., Even if it were true that “the alteration 
must be very slight, if not quite insignificant,” there 
would here be a rift in the lute, which must finally 
stop any further harping on the subject of Evolution. 

From the point of view of this theory, then, there 
is only one interpretation open,—viz., that a bud- 
variation is ultimately due to a peculiar admixture 
of germ-plasms in the seed from which the bud was 
ultimately derived. But the objections to entertaining 
this as even a logically possible explanation of the 
phenomena in all cases, is insuperable. 

In the first place, such a variation, when it does 
arise, is usually a variation of an extremely pronounced 
character ; therefore it is very far from supporting 
Weismann’s view, that the “alteration” of germ-plasm 
which is needed to produce it “must be very slight, 
and perhaps quite insignificant.” In most cases where 

H 


98 An Examination of Weismannism. 


jt occurs bud-variation presents so extreme a departure 
from the normal type, that no other kind of variation 
can be fitly compared with it in this respect. In 
particular, the degree of variation is usually very 
much greater than that which customarily obtains in 
congenital variations of the ordinary kind ; and, there- 
fore, if these be supposed due to particular admixtures 
of germ-plasm in sexual propagation, much more 
must those admixtures which give rise to sporting 
buds be characterized by peculiarities of no “insigni- 
ficant” order. And much more, therefore, ought 
they to assert themselves in sister-buds developed 
from the same individual seed (ovule), than we find 
to be the case with any sister-organisms which are 
developed from different individual seeds. Yet, in the 
second place, so far is this from being the case, that 
the most remarkable feature connected with bud- 
variation—next to the suddenness and extreme amount 
of the variation itself—is the usually isolated nature 
of its occurrence. There may be thousands of other 
buds on the same plant, and yet it is one bud alone 
that deviates so suddenly and so widely from its 
ancestral characters. Nay, more, a single bud-varia- 
tion may—and usually does—occur in plants which 
are habitually propagated by cuttings and graftings ; 
so that there may not only be thousands, but millions 
of buds all der:ved from one original seed, and all for 
many years remaining perfectly true to their parent 
type, with the single exception of the sporting bud, 
which, while it departs so widely from that type, is 
usually capable of transmitting its extraordinary char- 
acters indefinitely by a-sexual, and not infrequently 
also by sexual, methods. So that, altogether, it seems 


Wersmann's theory of Evolution (1891). 99 


impossible to suppose that in millions and millions of 
sister-buds, which through years and years exhibit no 
variation, a highly peculiar admixture of germ-plasm 
(which was originally present in the parent-seed) 
should have been latent; that it should then suddenly 
become so patent in a single bud, after which it never 
occurs in any other bud, save in the progeny of the 
sporting one. 

On the whole, then, while it thus seems impossible 
to attribute all cases of bud-variation to mixtures of 
germ-plasms in sexual propagation, the theory of 
germ-plasm is unable to entertain any other explana- 
tion, on pain of surrendering its postulate touching 
the unalterable stability of germ-plasm, on which the 
Weismannian theory of evolution is founded. 

So much for Weismann’s evidence touching the 
extreme, or virtually everlasting, stability of germ- 
plasm. We have seen that this evidence is not merely 
of a very poor character per se, or on antecedent 
erounds; but that it is directly negatived as evidence 
by the a-sexual origin of species in the plants alluded 
to by Professor Vines ; by certain facts which prove so 
high a degree of instability on the part of this hypo- 
thetical substance, that in some cases it admits of 
being very considerably modified in the course of 
only two or three generations by exposure to changed 
conditions of life ; while in other cases it may “ sport,” 
so as to produce “hereditary individual variations,” 
which are much more pronounced than any of those 
that ordinarily result from a blending of hereditary 
qualities in an act of sexual union. 


It will be well to conclude our examination of 
H+ 


100) 6 An Examination of Wetsmannism. 


Weismann’s system by stating exactly the effect 
produced on his theory of evolution by the foregoing 
disproof of its fundamental postulate—the absolute 
stability of germ-plasm. 

Clearly, in the first place, if germ-plasm has not 
been absolutely stable “since the first origin of sexual 
propagation,” the hereditary characters of germ-plasm 
may have been modified any number of times, and 
in always accumulating degrees. It matters not 
whether the modifications have been due mainly to 
external or to internal causes. It is enough to have 
shown that modifications occur. For, it will be re- 
membered, the doctrine of the absolute stability of 
germ-plasm is, that inasmuch as the “molecular” 
structure of germ-plasm cannot be affected either 
from without or from within, the only source of 
“hereditary individual variations” is to be found in 
admixtures of germ-plasms taking place in sexual 
fertilization. Slight “molecular” differences having 
been originally impressed upon different masses of 
germ-plasm when these were severally derived from 
their unicellular sources, so unalterable has been the 
stability of germ-plasm ever since, that-these slight 
“molecular” differences have never been in any 
degree effaced; and although in sexual unions they 
have for untold ages been obliged to mix in ever- 
varying proportions, they still continue—and ever 
must continue—to assert themselves in each ontogeny. 
Therefore, as Weismann himself formulates this 
astonishing doctrine,—* The origin of hereditary in- 
dividual variations cannot indeed be found in the 
higher organisms, the Metazoa and Metaphyta ; but 
is to be sought for in the lowest—the unicellular 


Weismann's theory of Evolution (1891). 101 


organisms.” Or again,— “The formation of new 
species, which among the lower Protozoa could be 
achieved without amphigony, could only be attained 
by means of this process in the Metazoa and Meta- 
phyta. It was only in this way that hereditary 
individual differences could arise and persist }.” 

Now this doctrine is the most distinctive, as it is 
the most original feature in Weismann’s system of 
theories. That it is of interest as an example of 
boldly carrying the premises of a theory to their 
logical termination, no one will deny. But as little 
can it be denied that the very stringency of this logical 
process brings the theory itself into collision with such 
facts as those which have now been stated, and which, 
as far as I can see, are destructive of the theory—or, 
at any rate, of all that side of the theory which 
depends on the doctrine of absolute stability. 

Take, for instance, the sequent doctrine that natural 
selection is inoperative among the unicellular or- 
ganisms. Here, indeed, we have another of those 
doctrines which are so improbable on merely ante- 
cedent grounds, that their presence might well be 
deemed a source of irremediable weakness to the 
whole theory of evolution of which they form integral, 
or logically essential, parts. For seeing that the 
rate of increase in most of the unicellular organisms 
is quite as high as—and in most cases very much 
higher than—the rate that obtains in any of 
the multicellular, it becomes on merely antecedent 
grounds incredible that the struggle for existence 
should here wot lead to any survival of the fittest. 
When, for instance, we learn from Maupas that 

Essays, p. 296. 


102 An Examination of Wersnannism. 


a single Stylonichia is potentially capable of yield- 
ing a billion descendants within a week, we should 
need some extraordinarily good evidence to make 
us believe that as regards this organism natural 
selection is inoperative. But the point at present is 
that, quite apart from all general and a@ friorz con- 
siderations of this kind, Weismann’s doctrine that 
unicellular organisms cannot be influenced by natural 
selection must be abandoned. For this doctrine 
followed deductively from the premiss that in the 
multicellular organisms congenital variations can only 
be due to admixtures of germ-plasms in acts of 
sexual fertilization ; so that, in the absence of such 
admixtures, there could be no material for natural 
selection to work upon. But now we have found that 
this premiss must be given up; and, therefore, the 
deduction with respect to the unicellular organisms 
falls to the ground. Although it is true that the 
unicellular organisms propagate by fission, and 
although we grant, for the sake of argument, that 
they never propagate by way of sexual unions—even 
so this can no longer be taken to argue that none of 
their innumerable species owe their origin to natural 
selection. And, although it is probably true that the 
sexual methods of propagation constitute one source 
of hereditary individual variation among the multi- 
cellular organisms, there is no vestige of any indepen- 
dent reason for supposing that this is the ovly source 
of such variation; while the sundry facts which have 
now been given amount to nothing short of a demon- 
stration to the contrary’. 


1 In this connexion it ought to be observed that Darwin believed 
the causes of variation to be internal as well as external—or arising 


Sumnary. 102 
re) 


Lastly, and as regards the multicellular organisms, 
it is evident that Weismann's essay Ox the Significance 
of Sexual Reproduction in the Theory of Natural 
Selection must be cancelled. For, apart from the 
contradictory manner in which this matter has been 
stated (pp. 70, 93, notes), and apart also from the con- 
sideration that other and quite as probable reasons 
have been suggested for the origin of sexual repro- 
duction, there is the fact that Weismann’s theory is 
no longer tenable after the above destruction of its 
logical postulate in the absolute stability of germ- 
plasm. For, in the absence of this postulate, there is 
no basis for the theory that admixtures of germ- 
plasms in sexual reproduction furnish the sole means 
whereby heritable variations can be supplied for the 
working of natural selection. 


Summary. 


THE theory of germ-plasm is not only a theory of 
heredity: it is also, and more distinctively, a theory 
of evolution. Asa theory of heredity it is grounded 
on its author's fundamental postulate—the continuity 
of germ-plasm; and, further, on a fact well recog- 
nized by all other theories of heredity, which he 
expresses by the term stability of germ-plasm. But 
as a theory of evolution it requires two additional 
postulates for its support—viz., that germ-plasm has 


from ‘‘the nature of the organism” no less—or even more—than from 
‘changed conditions of life.’ But although he appears to have enter- 
tained the admixture of hereditary endowments in sexual unions as one 
of the causes of variation belonging to the former category, he expressly 
says that he didnot regardit as the only, or even the main, cause. (See 
Variation, &c., vol. i, pp. 197, 398; vol. ii, pp. 237, 252+) 


104 Ax Examination of Wetsmannism. 


been perpetually continuous “since the first origin of 
life,” and absolutely stable “since the first origin of 
sexual reproduction.” It is clear that these two 
additional postulates are not needed for his theory of 
heredity, but only for his additional theory of evolu- 
tion. There have been other theories of heredity, 
prior to this one, which, like it, have been founded on 
the postulate of “ continuity” (in Weismann’s sense) of 
the substance of heredity; but it has not been needful 
for any of these theories to postulate further that this 
substance has been a/ways thus isolated, or even that 
it is now zzvariably so. For even though the isolation 
be frequently invaded by influences of body-changes 
on the congenital characters of this substance, it does 
not follow that the body-changes must be transmitted 
to offspring exactly as they occurred in parents. They 
may produce in offspring what we have agreed to call 
“specialized” hereditary changes, even if they never 
produce “representative” hereditary changes,—i.e., 
the transmission of acquired characters. But it is 
essential to Weismann’s theory of evolution that body- 
changes should not exercise a modifying influence 
of any kind on the ancestral endowments of this 
substance; hence, for the purposes of this further 
theory he has to assume that germ-plasm presents, 
not only conzzinuzty, but continuity wxbroken since the 
jirst origin of life. 

Similarly as regards his postulate of the stability of 
germ-plasm as adsolute. It is enough for all the 
requirements of his theory of heredity, that the sub- 
stance in question should present the high degree of 
stability which the facts of atavism, persistence of 
vestigial organs, &c., prove it to possess. But for his 


Summary. 105 


further theory of evolution it is necessary to make 
this further postulate of the stability of germ-plasm 
as undisturbed since the first origin of sexual propaga- 
tion: otherwise there would be no logical foundation 
for any of the distinctive doctrines which go to 
constitute that theory. 

Thus much understood, we proceeded to examine 
the theory of germ-plasm in each of its departments 
separately—i.e., first as a theory of heredity, and 
next as a theory of evolution. And we begun by 
comparing it as a theory of heredity with the pre- 
ceding theories of Darwin and Galton. In the result 
we found that germ-plasm resembles gemmules in all 
the following respects. Itis particulate; constitutes the 
material basis of heredity; is mainly lodged in highly 
specialized cells; is nevertheless also distributed 
throughout the general cellular tissues, where it is 
concerned in all processes of regeneration, repair, and 
a-sexual reproduction; presents an enormously com- 
plex structure, in that every constituent part of 
a potentially future organism is represented in a fer- 
tilized ovum by corresponding particles; is every- 
where capable of virtually unlimited multiplication, 
without ever losing its hereditary endowments; is 
often capable of carrying these endowments in a dor- 
mant state through a long series of generations, until 
at last they re-appear again in what we recognize as 
reversions. Such being the points of resemblance, the 
only points of difference may be summed up in the 
two words—continuity, and stability. For, as regards 
continuity, while Darwin’s theory supposes the sub- 
stance of heredity to be more or less formed anew in 
each generation by the body-tissues of that generation, 


106 An Examination of Wersmanntsme. 


Weismann’s theory regards this substance as owing 
nothing to the body-tissues, further than lodgement 
and nutrition. Therefore, while the theory of gem- 
mules can freely entertain the doctrines of Lamarck, 
the theory of germ-plasm excludes them as physio- 
logically impossible, in all cases where sexual repro- 
duction is concerned. Again, as regards stability, 
while Darwin’s theory simply accepts the fact of such 
a degree of stability appertaining to the substance of 
heredity as the phenomena of atavism, &c. prove, 
Weismann’s theory postulates the stability of this 
substance as absolute. But, as we have now so often 
seen, he does so in order to provide a hypothetical 
basis for his further theory of evolution. In as far as 
his theory of heredity is concerned, there is no reason 
why it should differ from Darwin’s in this respect. 
Again, comparing Weismann’s theory of heredity 
with that of Galton, we found that germ-plasm 
resembies stirp in all the points wherein we have just 
seen that it resembles germ-plasm. Or, otherwise 
stated, all three theories are thus far coincident. But 
cerm-plasm resembles stirp much more closely than 
it does gemmules, seeing that the theory of stirp is 
founded on the postulate of “continuity” in exactly 
the same manner as is the theory of germ-plasm. In 
point of fact, the only difference between these two 
theories consists in the two further postulates presented 
by the latter—viz., that the “continuity ” in question 
has been unbroken since the origin of life, while the 
“stability ” in question has been uninterrupted since 
the origin of sexual propagation. But seeing that 
both these additional postulates have reference to 
Weismann’s theory of evolution, we may say that his 


Summary. 107 


theory of heredity is, as regards all essential points. 
indistinguishable from that of Galton. 

The truly scientific attitude of mind with regard to 
the problem of heredity is to say, as Galton says. 
“that we might almost reserve our belief that the 
structural [i.e., somatic] cells can react on the 
sexual elements at all, and we may be confident that 
at most they do so in a very faint degree; in other 
words, that acquired modifications are barely, if at 
all, zzherzted, in the correct sense of that word.” But 
for Weismann’s further theory of evolution, it is 
necessary to postulate the two additional doctrines 
in question; and it makes a literally immeasurable 
difference to the theory of evolution whether or not 
we entertain these two additional postulates. For no 
matter how faintly or how fitfully the substance of 
heredity may be modi%ted by somatic tissues, by 
external conditions of life, or even by so-called 
spontaneous changes on the part of this substance 
itself, numberless causes of congenital variation are 
thus admitted, while even the Lamarckian principles 
are hypothetically allowed some degree of play. And 
although this is a lower degree than Darwin supposed, 
their influence in determining the course of organic 
evolution may still have been enormous; seeing that 
their action in any degree must always have been 
directive on the one hand, and cumulative on the 
other. 

Having thus pointed out the great distinction 
between the theories of stirp and of germ-plasm, 
it became needful to note that Weismann himself 
is not consistent in observing it. On the con- 
trary, in some passages he apparently expresses 


108 An Examination of Wersmannism. 


himself as willing to resign both his distinctive postu- 
lates—continuity as perpetual, and stability as absolute. 
But it is evident that such passages must be ignored 
by his critics, because, although as far as his theory 
of heredity is concerned they betoken an approach to 
the less speculative views of Galton, any such approach 
is proportionally destructive of his theory of evolution. 
It must not be supposed that I am taking an 
ungenerous advantage of these occasionally funda- 
mental concessions. On the contrary, one cannot but 
admire the candour which they display. But, as 
I have said, it is necessary for us to ignore them, if 
only in order to examine the Weismannian theory of 
eerm-plasm as a distinctive theory at all. And more 
than this. Seeing that his theory of heredity differs 
from Galton’s chiefly in being further an elaborate 
theory of evolution (founded on the two additional 
postulates in question), my main object has been to 
show the enfeeblement of the former which Weis- 
mann has caused by his addition of the latter. If he 
were to express his willingness to abandon his theory 
of evolution for the sake of strengthening his theory of 
heredity by identifying its main features with those of 
Galton’s, personally I should have no criticism to pass. 
Indeed, I was myself one of the first evolutionists who 
called in question the Lamarckian factors; and ever 
since the publication of Galton’s theory of heredity at 
about the same time, I have felt that in regard to its 
main principles—or those in which it agrees with 
Weismann’s—it is probably the true one. But I can 
nowhere find that Weismann is thus prepared to 
surrender his theory of evolution. Occasionally he 
plays fast and loose with the two additional postulates 


Summary. 109 


on which this theory is founded; but he does so 
without appearing to perceive the speculative im- 
possibility of any longer sustaining his temple of 
evolution if he were to remove its pillars of germ- 
plasm. 

Ignoring, then, these inconsistencies, we proceeded 
to examine separately, and on their own respective 
merits, the two distinctive postulates of the theory 
of germ-plasm—ferpetual continuity since the first 
origin of life, and adsolute stability since the first 
origin of sexual propagation. 

It does not appear to me that very much has to 
be said, either for or against the former postulate, 
on merely antecedent grounds, or grounds of general 
reasoning. Therefore I relegated to an Appendix 
my examination of what Weismann has argued on 
these grounds, while in the text I considered only 
what he has advanced as evidence a posteriorz. Here, 
as we saw, he has developed three distinct lines of 
verification—viz. (A) the migration of germ-cells in 
some of the A/ydromedusae, (B) the early separation 
of germ-cells in the ontogeny of certain Invertebrata, 
and (C) the alleged invariability of organisms which 
are produced parthenogenetically. But we have seen, 
with respect to (A), that the specialized character 
of germinal cells is a fact which every theory of 
heredity must more or less recognize ; and, therefore, 
that the migration of these cells, wherever it may be 
found to occur, does not lend any peculiar countenance 
to Weismann’s theory. There may be many reasons 
for such migration other than the one which this 
theory assigns; while the reason which it does assign 
is rendered improbable by the consideration that in 


110 Ax Examination of Wetsmanntism. 


the Yydromedusae the material of heredity is already 
and richly diffused throughout the general tissues. 
(B) and (C) are both contrary to fact; and, therefore, 
in whatever measure they would have corroborated 
the theory had they proved to be true, in that 
measure must they be held to discountenance the 
theory now that they have been shown to be false. 

It appears, then, that there is no evidence in support 
of the postulate of the perpetual continuity of germ- 
plasm. There is nothing to show the necessary 
non-inheritance of acquired characters. The only 
evidence which one can recognize as good, is that which 
makes equally in favour of the theory of stirp—or 
rather, of the well-known fact that congenital charac- 
ters are at any rate much more heritable than are 
acquired: which, it is needless to repeat, is a widely 
different thing from proving—or even rendering prob- 
able — the adsolute restriction of germ-plasm to 
a separate “sphere” of its own “since the origin of 
lifes | 

But now, although there is no evidence in support 
of this postulate, there is no small amount of evidence 
against it. For this evidence goes to indicate that 
no small amount of reciprocal action habitually takes 
place between body-tissues and germinal elements: 
indeed it seems almost to prove that the orbits of 
germ-plasm and somato-plasm are not mutually 
exclusive, but touch and cut cach other to a con- 
siderable extent. The evidence in question, it will be 
remembered, is derived from the effects of puberty, 
senility, castration, &c. ; the occasional effect of pollen- 
ization on the somatic tissues of plants ; the influence 
which a stock occasionally exercises upon a scion, 


Sumnary. III 


or vice versa, which proves the possibility of a trans- 
mission of hereditary characters by a mere grafting 
together of somatic tissues; the direct evidence given 
by De Vries that in certain Algae constituents of 
cellular tissue pass immediately from the maternal 
ovum to the daughter organism ; and the evidence, 
both direct and indirect, which remains to be given 
on a larger scale in my subsequent volume, where we 
shall have to challenge the validity of Weismann’s 
fundamental postulate touching the non- occurrence 
of Lamarckian factors in any of the multicellular 
organisms. 

It must here again be noticed that in those passages 
where he concedes the possibly ‘ occasional” trans- 
mission of acquircd characters Weismann is anni- 
hilating his own theory, root and branch. Thus, for 
example, in allusion to De Vries’ observation just 
mentioned, he says that we cannot exclude the 
possibility of “changes being induced by external 
conditions in the organism as a whole, and then com- 
municated to the germ-cells after the manner in- 
dicated in Darwin’s hypothesis of pangenesis.” But 
it is obvious that the theory of germ-plasm mast 
“exclude the possibility of such a transmission occa- 
sionally occurring”; for the very essence of that 
theory consists in its postulating a difference between 
germ-plasm and the general body-substance zz kind, 
such that there never caz be any “communication” 
from the one to the other “after the manner indicated 
by Darwin’s hypothesis of pangenesis.” Any pre- 
varication over this point amounts simply to aban- 
doning the theory of germ-plasm altogether, and 
opening up a totally distinct issue—namely, the 


112 Ax Examination of Wersmanntsm. 


relative tmportance of natural selection and the 
Lamarckian factors in the process of organic evolution. 
It may be perfectly true—and I myself believe it 
is perfectly true—that Darwin attributed too large 
a measure of importance to the Lamarckian factors ; 
but whether or not he did so is quite a different 
question from that which obtains between his theory 
of pangenesis and Weismann’s theory of germ-plasm. 
The former question is whether we are to “modify” 
the theory of pangenesis, so as to constitute it the 
theory of stirp ; the latter question is whether we are 
to “abolish” the theory of pangenesis, in favour of its 
logical antithesis, the theory of germ-plasm. And 
this question remains to be dealt with in my next 
volume. 


Coming then, lastly, to the companion postulate 
of germ-plasm as absolutely stable since the first 
origin of sexual propagation, we.had to observe 
that, unlike the one we have just been considering, 
there is an immensely strong presumption against it 
on merely antecedent grounds. That the most com- 
plex substance in nature should likewise be the most 
stable substance with regard to complexity of ‘ mole- 
cular structure”; that the greater its complexity 
becomes the greater becomes its stability, so that 
while in the comparatively simple uniceliular organ- 
isms it is eminently susceptible of modification by 
external conditions, it entirely ceases to be thus 
susceptible when it becomes evolved into the incom- 
parably more complex and immensely more varied 
structures which form the bases of heredity in the 
multicellular organisms—where, also, it must come 


Summary. 113 


into ever more and more intricate as well as more and 
more diverse relations with the external world ;—all 
this is, I repeat, well nigh incredible. At any rate, 
speaking for myself, I should require some enormous 
weight of evidence to balance so enormous an ante- 
cedent improbability, or before I could regard such 
a doctrine as meriting any serious attention. 

What, then, is the evidence that has been adduced ? 
We have found that this evidence is zz/. On the 
other hand, we have found that the evidence against 
the doctrine is abundantly sufficient to annihilate the 
doctrine—and this quite apart from all the antecedent 
considerations just alluded to. For not only have we 
the sundry facts of bud-variation, a-sexual origin of 
species, &c., which contradict the doctrine ; but we 
have also the results of direct experiment, which 
prove that the alleged stability of germ-plasm may be 
conspicuously upset by slight changes in the external 
conditions of life. So that both from within and from 
without the stability which is alleged in theory admits 
of being overturned by facts. 

And here, in order to avoid all possible confusion, 
I must ask it once more to be noted that there is not, 
and never has been, any question touching the “igh 
degree of stability which is exhibited by whatever 
substance it is that constitutes the material basis of 
heredity. But this is a widely different thing from 
supposing the stability absolute, so that it can never 
have been affected in any degree since the first origin 
of multicellular organisms, or in any of the millions of 
species into which these organisms have ramified. 
And the fact that in some cases we are actually 
able to observe a change of congenital characters as 

I 


114. An Examination of Wetsmanntsm. 


resulting from some “ spontaneous” change in the 
hereditary material itself (as in bud-variation), or from 
some change in the external conditions of life (as in 
Hoffmann’s experiments)—this fact is more than is 
required in.order finally to overthrow the intrinsically 
untenable doctrine which is in question. 

Now, with the collapse of this doctrine there 
collapses also the important chain of deductions 
therefrom, which together constitute Weismann’s new 
theory of evolution. In particular, that natural selec- 
tion is the exclusive means of modification among all 
the Metazoa and Metaphyta, while it is as exclusively 
ruled out with respect to all the Protozoa and Pro- 
tophyta ; that individual variations among the former 
can only be determined by sexual unions, while among 
the latter they can only be determined by the direct 
action of the environment; that the origin of con- 
genital variability in all the Metazoa and Mctaphyta 
is to be sought, and can only be found, in variations 
which occurred millions of years ago in the Protozoa 
and Protophyta; that the “significance of sexual 
propagation” is to be found in the view, that by this 
means alone can congenital variations have been ever 
since produced ; &c., &c. 


Upon the whole then, it appears to me that both 
the fundamental postulates of the theory of germ- 
plasm are unsound. That the substance of heredity 
is largely continuous and highly stable I see many 
and cogent reasons for believing. But that this sub- 
stance has been uninterruptedly continuous since the 
origin of life, and absolutely stable since the origin 
of sexual propagation, I see even more and better 


Summary. 115 


reasons for disbelieving. And inasmuch as these two 
latter, or distinctive, postulates are not needed for 
Weismann’s theory of heredity, while they are both 
essential to his theory of evolution, I cannot but 
regret that he should thus have crippled the former 
by burdening it with the latter. Hence my object 
throughout has been to display, as sharply as possible, 
the contrast that is presented between the brass 
and the clay in the colossal figure which Weismann 
has constructed. Hence, also, my emphatic dissent 
from his theory of evolution does not prevent me 
from sincerely appreciating the great value which 
attaches to his theory of heredity. And although I have 
not hesitated to say that this theory is, in my opinion, 
incomplete; that it presents not a few manifest 
inconsistencies, and even logical contradictions; that 
the facts on which it is founded have always been facts 
of general knowledge; that in all its main features it 
was present to the mind of Darwin, and distinctly 
formulated by Galton ; that in so far as it has been 
constituted the basis of a more general theory of 
organic evolution, it has clearly proved a failure :— 
such considerations in no wise diminish my cordial 
recognition of the services which its distinguished 
author has rendered to science by his speculations 
upon these topics. For not only has he been suc- 
cessful in drawing renewed and much more general 
attention to the important questions touching the 
transmissibility of acquired characters, the causes of 
variation, and so on; but even those parts of his 
system which have proved untenable are not without 
such value as temporary scaffoldings present in re- 
lation to permanent buildings. Therefore, if I have 
I 2 


116 An Examination of Wetsmannism. 


appeared to play the véle of a hostile critic, this has 
only been an expression of my desire to separate 
what seems to me the grain of good science from the 
chaff of bad speculation. And the candour which 
Professor Weismann has always displayed towards 
criticism of this character enables me to hope with 
assurance, that I have said nothing which he him- 
self will regard as inconsistent with high admiration 
of his work as a naturalist, or of his originality as 
a philosopher. 


Gil Pal DE Raa 


WEISMANNISM UP TO DATE (1893). 


HITHERTO we have been considering Professor 
Weismann’s system as it stood prior to the publica- 
tion of his most recent works on Amphimixis and The 
Germ-plasm, in 1891 and 1893 respectively. These 
later and highly elaborate essays present considerable 
modifications of the system, as it stood when the 
foregoing criticism was written. But, for reasons 
already stated in the Preface, it appears to me 
desirable to leave that criticism as it was originally 
constructed, and to supply this further chapter for 
the purpose of dealing with the large alterations of, 
and important additions to, the theory of germ-plasm, 
which the maturer thought of its gifted author has led 
him to announce. 

A few general remarks may be most conveniently 
made at the outset. 

In the first place, these recent publications present 
the advantage over their predecessors of being sys- 
tematic treatises, instead of more or less independent 
papers. On this account they present a logical 
sequence of thought, which renders the task of ex- 
amination much less difficult than it was in the case 
of the first volume of the /ssays. 


118 An Examination of Wersmannism. 


In the second place, as a result of his more matured 
reflection, Professor Weismann has himself perceived 
a considerable number of the difficulties and objections 
which I have set forth in the preceding chapters. 
And not only has he thus anticipated many of my 
criticisms; but, as a result of doing so, he has changed 
not a few of the most important parts of his previous 
system, with the result of greatly improving it. 

But, in the third place, notwithstanding that his 
remarkable power of speculative thinking is every- 
where united with adequate knowledge in the sundry 
branches of biological science with which it deals, 
I confess to a serious doubt whether it has not been 
permitted to enjoy an undue amount of liberty. If 
only they can be laced together by a thread of logical 
connexion, hypotheses are added to hypotheses in 
such profusion as we are acquainted with in the works 
of metaphysicians, but which has rarely been ap- 
proached in those of naturalists. The whole mechanism 
of heredity has been now planned out in such minute- 
ness of detail and assurance of accuracy, that in reading 
the account one is reminded of that which is given 
by Dante of the topography of Inferno. For not 
only is the “sphere” of germ-plasm now composed 
of nine circles (molecules, biophores, determinants, ids, 
idants, idio-plasm, somatic-idioplasm, morpho-plasm, 
apical-plasm), but in most of these regions our guide 
is able to show us such strange and interesting phe- 
nomena, that we return to the fields of science with 
a sense of having been indeed in some other world. 
Or, to change the metaphor, if it be the case that 
“a true scientific judgement consists in giving a free 
rein to speculation with one hand, while holding 


Wersmannism up to date (1893). 119 


ready the break of verification with the other,” I think 
it must be admitted that, in as far as he has erred, 
Professor Weismann has done so by driving a chariot 
which is unprovided with any break at all. 

Hence, fourthly, it is needless to follow, even in 
epitome, the innumerable windings of these never- 
ending speculations. For, on the one hand, it would 
be impossible to do so without adding an unduly 
extended chapter to our already tediously prolonged 
consideration of Weismann’s views; while, on the 
other hand, we should have to deal merely with matters 
of comparative detail. The additions which have 
been made to his theory by his most recent publica- 
tions are chiefly concerned with the matter just 
alluded to—viz., a minute elaboration of the hypo- 
thetical mechanism of heredity, in accordance with 
the general theory of germ-plasm. Without question 
this elaboration is everywhere thoughtful, and often 
highly ingenious; but until the general theory in 
question shall have been satisfactorily grounded, it 
seems premature to supply so immense a design of 
purely deductive construction. Beautiful though it 
may be in its imposing elevation, this drawing of “the 
architecture of germ-plasm” must be regarded as 
a work of artistic imagination rather than as one of 
scientific generalization. From the latter point of 
view it is at most a temple 27 fosse, and even if it is 
ever to be realized 727 esse, we cannot allow the actual 
building to begin until we are much more sure than 
anybody is at present entitled to be touching the 
foundations on which it is proposed to rear so great 
an edifice. 

Again, and fifthly, even if Weismann should ever be 


120 An Examination of Wetsmannism. 


able to satisfy us upon this matter, or fully to demon- 
strate his basal proposition touching the perpetual 
continuity of germ-plasm, there would still be a far cry 
between accepting this sufficiently simple proposition 
and supposing that there is any adequate reason for 
entertaining so complex a scheme of the structure of 
germ-plasm. No doubt Weismann himself would be 
quite ready to admit, that from his basal proposition 
of the cortinuity of germ-plasm it is logically possible 
to construct many other designs of the architecture of 
ecrm-plasm, besides the one which he has so beautifully 
drawn. And although most of such alternative designs 
would doubtless embody some one or other of the 
features which are presented by his own, no one could 
say which features common to any two of the designs 
represent the facts. For in the case of all alike 
there would be a necessary absence of verification: 
the architects would all and equally have to ac- 
knowledge that their imposing pictures of “the palace 
of truth” were but imaginary. Such, in my opinion, 
has been the case with all theories of the ultimate 
mechanism of heredity hitherto published; but the 
difference between them and Weismann’s theory in 
this respect is, that while most of the others have not 
gone into speculative details further than was necessary 
as a means of substantiating their basal postulates, 
Weismann’s, as now developed in 7he Germ-plasm, is 
mainly concerned with such speculative details as an 
end, or object fer se. 

But, it may be replied, by thus constructing an 
ideal mechanism of heredity Weismann is greatly 
strengthening his fundamental postulate of the con- 
tinuity of germ-plasm, because he shows how all the 


Weismannism up to date (1893). 121 


main facts of heredity, and allied phenomena, admit 
of being explained if once the postulate be accepted. 
If this were urged, however, I should have two remarks 
to offer. The first is that Weismann, in constructing 
his ideal mechanism, has gone very much further in 
the way of elaboration than can possibly be required 
for this purpose. So much further, indeed, that his 
purpose has evidently been the constructing of his 
ideal mechanism, as I have just said, for its own sake, 
and not for the sake of substantiating its basal pro- 
position by showing how well the latter can be made 
to work in explaining the phenomena of heredity, &c. 
Moreover—and this is my second remark—however 
well the basal proposition may be made to work in 
this respect, we must not be deceived into supposing 
that such a fact is equivalent to a substantiation of 
the proposition. This proposition—the continuity of 
germ-plasm—is the inverse of that which constitutes 
the basis of the theory of pangenesis. For while the 
latter assumes that in the last resort it is always 
somatic tissues which produce the substance of 
heredity, the former simply inverts the terms of this 
assumption, and holds that it is always the substance 
of heredity which produces the somatic tissues. Now, 
in all cases where one theory consists in thus simply 
inverting the terms of another, it will be found that 
the facts which they both scek to explain lend 
themselves equally to explanation by either, up to 
some certain and usually distant point, where a crucial 
test becomes possible. Take, as an example, the 
geocentric and heliocentric theories of the solar 
system. Here the question was whether the earth 
moved round the sun, or vice versa; and so many of 


122 An Examination of Wetsmannism., 


the facts of observation lent themselves equally well 
to either interpretation, that it was very many centuries 
before the crucial tests were forthcoming. So, in the 
present instance, the question is as to whether the 
carriers of heredity move from body-cells to germ- 
cells, or vice versa; and it is because the theory 
which sustains the latter view has merely to invert 
the terms of the one which takes the former, that so 
many of the facts of observation lend themselves 
equally well to both—as we have seen in chapter III 
(pp. 56-59). 

Lastly, yet another reason for not considering in 
any detail Professor Weismann’s intricate speculations 
on the ultimate mechanism of heredity is, that by so 
doing I should have found it impossible to avoid 
obscuring the main issues. For even Professor Weis- 
mann himself, by the extreme care which he has 
taken in fully presenting his scheme of this ultimate 
mechanism, has not found it practicable to keep 
distinctly before our view the relative insignificance 
of such details, as compared with the fundamental 
importance of his original postulates. Hence, I have 
deemed it best in the present chapter to restrict our 
attention to the changes which he has recently made 
in these the foundations of his entire system. 

For these reasons, then, I will mention only those 
main features in the “architecture of germ-plasm ” 
which it is necessary to understand for the purposes of 
the following criticism touching the general theory of 
germ-plasm in the most recent phase of its evolution. 


To begin with, Weismann has now seen the desira- 
bility of ceasing to designate the ultimate “carriers of 


Wetsmannism up to date (1893). 123 


heredity ” by the term “molecules.” Indeed, in these 
later volumes he has fully anticipated my remarks 
touching the use of this term in his previous “ Essays 1.” 
The result of his more mature reflection may be 
presented in epitome thus. 

A number of ‘‘ molecules,” in the proper or chemical 
sense of the word, go to form a “biophore,” which is 
the ultimate unit of living substance. 

A number of “biophores” go to form a “deter- 
minant, which is a special element in the germ-plasm, 
capable of directing the ontogeny of such and such 
a group of cells as is independently variable from the 
germ onwards. 

A number of “determinants” go to form an “id,” 
which is the same hypothetical body as Weismann 
has hitherto designated by the term “ancestral germ- 
plasm.” That is to say, it is a group of determinants 
indissolubly united in phylogeny, and_ therefore 
transmitted by heredity as one complex whole. Ids 
are, perhaps, microscopically visible; and, if so, they 
probably correspond to the small granules (micro- 
somata), which are familiar to the histologist in the 
structure of chromosomes. 

A number of “ids” go to form an “idant,” which 
is a chromosome, or chromatin fibre’. 

In my opinion the most important advance which 
Weismann has made in his theory by means of this 
scheme has reference to the third of these divisions— 
the determinant. It is a matter of observation that 
every cell of a multicelluar organism does not vary 


1 See above, p. 54, note. 
2 See Darwin and after Darwin, Part I, p. 129. 


124 An Examination of Wersmannism. 


independently : it appears to be always the case that 
in the phenomena of variation a smaller or a larger 
group of cells is concerned. Now there must be 
something that determines the similar and simul- 
taneous variation of such a whole group of cells; 
and, in all cases where such a variation is congenital, 
it is certain that this something must be contained 
in the substance of heredity. So far, I think, we 
must all agree, whether or not we regard this sub- 
stance as “germ-plasm.” In other words, whether 
we regard the carriers of heredity as proceeding 
centrifugally (germ-plasm) or centripetally (gemmules), 
it seems to me that we ought to accept Weismann’s 
doctrine of determinants. Indeed, pathologists have 
already furnished a foreshadowing of such a doctrine 
in regard to the phenomena presented by certain 
diseases, such as cancer ; but it is an important step 
to have extended the idea from pathology to biology 
in general—and, at the same time, to have given it 
a more definite shape than it has hitherto presented. 
In Weismann’s hands it serves to render more con- 
ceivable—if not also more intelligible—that process 
of marshalling cell-formations, which, be our theories 
what they may, is assuredly the most distinctive and 
remarkable fact of ontogenetic organization. 

Again, as regards the id, I do not see how any one 
can attentively read Professor Weismann’s discussion 
without acknowledging that, if we once accept his 
doctrine of determinants, his sequent doctrine of ids 
becomes a logical necessity. 

On the other hand, however, I do not see that 
such is the case with respect to idants ; and still less 
do I see any reason for identifying the latter with 


Wetsmannism up to date (1893) 125 


chromosomes—even assuming that chromosomes are 
the visible repositories of the carriers of heredity !. 

Referring the reader to Weismann’s own exposition 
for a full account of these and many others additions 
to his general theory of germ-plasm, I will at once 
proceed to consider the alterations or emendations of 
that theory which have been published in his last two 
volumes, and which, as we shall find, have in large 
measure anticipated some of the most important points 
in the foregoing criticism. Therefore in the following 
criticism I will consider serzatzm what he has now said 
touching all these points, and conclude by offering 
some general remarks on the resulting position of his 
general system of theories up to the present date. 

Pursuing the same method of criticism as that 
adopted in the preceding chapters, we will first con- 
sider the further modifications of Weismann’s theory 
of heredity, and next those of his theory of organic 
evolution. 


Weismann’s theory of ‘Heredity (1893). 


First of all, Weismann has now profoundly modified 
his theory of polar bodies. For, owing to certain 
more recent researches of Professor O. Hertwig, he 
very candidly allows :—*‘ My previous interpretation 
of the first polar body as the removal of ovogenetic 
nucleo-plasm from the egg must fall to the ground: 


2% 


about this there is no possible doubt *. 


1 Tt must always be remembered that the view adopted by Weismann 
touching the nucleus (and more especially the chromosomes) of a germ- 
cell being the sole seat of heredity, is still far from having been estab- 
lished. 

2 Essays, vol. ii. p. 122. 


126 An Examination of Wetsmanunism. 


He now regards both polar bodies as concerned in 
the same function of removing superfluous germ-plasm. 
Therefore one-half of his previous theory is abandoned : 
“the ovogenetic idio-plasm” is now supposed to be 
simply absorbed in the course of ontogeny, as I had 
suggested in one of the preceding chapters (pp. 42-46). 
The consequence is that he has now nothing to oppose 
to the view which is likewise there suggested (pp. 43- 
44)—viz., that his whole theory of polar bodies is 
rendered needless and improbable by the fact that the 
very mode in which ova are produced renders ample 
provision for the removal of any amount of superfluous 
gverm-plasm which the theory of germ-plasm may 
require. 

It is needless to say, after what has already been 
said in the pages just referred to, that in my opinion 
Professor Weismann has improved his main system 
of theories by dropping this part of his subordinate 
and, for the most part. separate theory of polar bodies. 
I only wish he could have seen his way to dropping 
the whole. 


Again, he has now fully considered the phenomena 
of repair, regeneration, reproduction from somatic 
tissues, budding, and graft-hybridization. 

Touching the four former he takes the view which 
I have supposed that he would (p. 53). As regards the 
latter, he fully accepts the fact of an occasional trans- 
mission of characters from one species or variety of 
plant to another by mere grafting’. But, although the 
explanation which he gives of this fact may pass 
muster so far as the only case which he deals with in 

1 The Germ-plasm, p. 342. 


Wetsmannism up to date (1893). 127 


detail is concerned, I do not see how it can do so 
to many others. For the case which he considers is 
that of Cystzsus adam, where a bud of one species 
of Laburnum having been inserted in the wood of 
another produced a shoot which presented inter- 
mediate characters; and these have ever since been 
propagated by cuttings. Weismann’s interpretation of 
the facts here is, “that they were due to an abnormal 
kind of amphimixis, so that the idants of both species 
were combined in the apical cell of the first shoot !.” 
Now, although this explanation may well apply to 
a case of graft-hybridization by means of buds, it 
obviously cannot do so to any case where hybridization 
is produced by the grafting of woody tissues. For 
here there is no “apical cell” in the question; and 
therefore the difficulties which I have adduced on 
page 82 remain. Possibly Weismann may dispute 
the fact of hybridization in any of these cases; but, 
as he has not expressly done so, I will not go into 
the question of evidence *. 


One important addition to this side of Weis- 
mann’s system has been made in order to meet 
the class of difficulties which are presented by the 
apparent inheritance of certain climatic variations, as 
already mentioned on pp. 67-8. For example, his 
own butterflies seemed to render definite proof of 
somatogenetic variations caused by changed con- 
ditions of life being transmitted to progeny. There- 
fore, it will be remembered, Weismann candidly 
admitted, “even now I cannot explain the facts 
otherwise than by supposing a passive acquisition of 

1 The Germ-plasm, p. 342. 2 See, however, p. 83, note. 


128 An Examination of Wetsmannism. 


characters produced by the direct influence of 
climate ’’—i.e., an exactly representative copying in 
progeny of characters acquired by parents. I have 
already quoted these words in order to show their 
logical inadmissibility as used by Weismann. He 
cannot be allowed thus to entertain the Lamarckian 
factors and at the same time to maintain his theory 
of germ-plasm, which excludes them as physiologically 
impossible. Doubtless he was himself aware of this, 
for he immediately added that “ new experiments will 
be necessary to afford the ¢vwe explanation }.” 

The explanation, however, which he now gives is 
not based on any new experiments, but on a new 
suggestion to the effect that all such seemingly 
conclusive instances of the inheritance of acquired 
characters are, in truth, illusory. This suggestion is 
that “ Many climatic variations may be due wholly 
or in part to the simultaneous variation of corre- 
sponding determinants in some parts of the soma, and 
in the germ-plasm of the reproductive cells.*” For 
example, if, as Weismann now supposes, determinants 
of the same kinds occur in the somatic tissues as well 
as in the germ-cells, when a particular spot occurs on 
a butterfly’s wing, it has been due to a particular kind 
of determinant which in the course of ontogeny was 
transmitted from the germ-cell for the express purpose 
of controlling the size and colour of the spot. But 
a residue of precisely similar determinants was re- 
served in the germ-cell (germ-plasm), for the purpose 
of determining a precisely similar spot in the next 
generation. Hence, if a rise of temperature, or any 
other external change, is capable of so acting on the 


1 Essays, vol.i. p. 101. Italics mine. 2 The Germ-plasm, p. 406. 


Wetsmannism up to date (1893). 129 


determinant in the soma as to cause it to impart an 
abnormal colour to the spot when formed, a similar 
change is likely to be simultaneously effected in the 
corresponding determinants which are lying dormant 
inthe germ-plasm. Therefore, when the latter become 
active in the ontogeny of the next generation, they 
will produce spots presenting the same variations as 
those of the preceding generation. Obviously, how- 
ever, there would not be here any transmission of 
acquired characters. The change would be “ special- 
ized,’ but not “representative.” — 

No doubt we have here a sufficiently ingenious 
method of circumventing an awkward class of facts. 
But I should like to make two observations with 
regard to it. 

In the first place, the suggestion is highly specu- 
lative, and has been advanced solely for the sake of 
saving the theory of germ-plasm. There are no facts 
adduced in its favour, and it could scarcely be enter- 
tained as in the least degree probable by any one 
who has not already accepted the theory in question. 
Hence, unless we are to embark on a course of 
circular reasoning, we must refuse to accept the 
explanation of hereditary climatic variation now 
offered, until it shall have been fully corroborated by 
the experimental enquiry to which Weismann says he 
is now submitting it. 

My second observation is, that the suggestion is 
not new; but appears to have been derived from 
Professor Weismann’s recent study of Mr. Galton’s 
Theory of Heredity. At all events, the suggestion is 
there presented with sufficient lucidity, thus :— 

It is said that the structure of an animal changes when he is 

K 


130 An Examination of Wetsmannism. 


placed under changed conditions; that his offspring inherit some 
of his change; and that they vary still further on their own ac- 
count, in the same direction, and so on through successive genera- 
tions, until a notable change in the congenital characteristics of the 
race has been effected. Hence, it is concluded that a change 
in the personal structure has reacted on the sexual elements. 
For my part, I object to so general a conclusion, for the fol- 
lowing reasons. It is universally admitted that the primary 
agents in the processes of growth, nutrition, and reproduction 
are the same, and that a true theory of heredity must so regard 
them. In other words, they are all due to the development 
of some germinal matter, variously located. Consequently, when 
similar germinal matter is everywhere affected by the same 
conditions, we should expect that it would be everywhere 
affected in the same way. ‘The particular kind of germ whence 
the hair sprang, that was induced to throw out a new variety 
in the cells nearest to the surface of the body under certain 
changed conditions of climate and food, might be expected to 
throw out a similar variety in the sexual elements at the same 
time. The changesin the germs would everywhere be collateral, 
although the moments when any of the. changed germs hap- 
pened to receive their development might be different’. 


This allusion to Mr. Galton’s Theory of Heredity 
leads me to consider what Professor Weismann has 
said with regard to it in this latest publication, 
where, for the first time, he has dealt with it. 
In my opinion he has done but scant justice to the 
views of his predecessor, and therefore I will occupy 
some considerable space in seeking to justify this 
opinion. 

As already stated, from the time that Mr. Galton 
published his theory I have felt that in its main con- 
tention it presents a probably true solution of the main 
problem of heredity—viz., to account for the contrast 


* Galton, loc, czt., pp. 343-344. 


Wetsmannism up to date (1893). 131 


between congenital and acquired characters in respect 
of transmissibility. And this solution, as likewise 
already stated, was substantially identical with that 
which Professor Weismann published in the next 
decade. Indeed, the only important difference be- 
tween these two theories of heredity is, that while 
Weismann’s excludes on deductive grounds the 
physiological possibility of the inheritance of acquired 
characters, Galton’s more judiciously leaves to be 
determined, by subsequent enquiry of the inductive 
kind, the question whether acquired characters are 
ever transmitted in faint degrees, or whether they are 
never transmitted atall. In addition to this important 
difference, however, there are certain others which 
seem to me of very little consequence, inasmuch as 
they have reference to speculations on the ultimate 
mechanism of heredity, or the intimate morphology 
and physiology of the carriers of heredity—specula- 
lations which it would be absurd to suppose can be 
other than purely conjectural. Therefore in my 
previous criticism I did not allude to these subordinate 
points of difference, but stated merely, in general 
terms, that Galton’s view of the ultimate mechanism 
in question was such as to leave room for the possi- 
bility of the occasional transmission of acquired 
characters. And in this respect, it still seems to me, 
his theory has an advantage over that of Weismann. 
No doubt the latter is a much more elaborate and 
highly finished piece of work; but beauty of ideal 
construction is no guarantee of scientific truth—as we 
shall presently find exemplified in a striking manner 
with regard to Weismann’s theory of evolution. And 
if his theory of heredity, in its final shape, is a much 
K 2 


132 An Examination of Wetsmannism. 


more precise, detailed, and logically coherent structure 
than any which has ever been framed in this depart- 
ment of biological thought, there is all the more reason 
to scan critically the fundamental postulate on which 
it rests. Hence I cannot help feeling that it will be 
time enough to consider minor differences between 
the two theories when the physiological possibility of 
the occasional transmission of acquired characters, as 
entertained by Galton’s theory, shall have been ruled 
out as demonstrably opposed to fact. 

Seeing, however, that Professor Weismann thinks 
otherwise, and appears to attach as much importance 
to differences concerning deductive mznutiae as he 
does to those concerning fundamental principles, 
I will here contrast the two theories somewhat more 
in detail than heretofore, and with special refer- 
ence to what he has now himself said touching their 
relationship. | 

It will be remembered that the primary or funda- 
mental difference just alluded to is, that while the 
theory of germ-plasm postulates an adsolute continuity, 
the theory of stirp postulates but a partial con- 
tinuity, of the substance of heredity. Hence, ac- 
cording to Weismann’s view, we must go back to 
the unicellular organisms for the origin of this sub- 
stance in the multicellular; and we must regard use- 
inheritance as physiologically impossible. On _ the 
other hand, according to Galton’s view, there is no 
necessity for us to do either of these things. The 
origin of stirp is to be found in the somatic tissues of 
the multicellular organisms themselves. Nevertheless, 
this theory differs greatly from pangenesis, in that the 
former supposes the origin of hereditary substance to 


Wetsmannism up to date (189°). 133 


be mainly given in the phylogeny of any group of 
multicellular organisms, while the latter supposes it to 
be given mainly in each oxfogeny. Galton’s theory is, 
that in each ontogeny only a small part of the stirp 
derived from parents is consumed in making the 
new organism—the larger part being handed over in 
trust for passing on to the next generation, in the 
same way as Weismann supposes to be the case with 
germ-plasm. Darwin’s theory, on the other hand, 
does not entertain any such notion of “continuity” 
in the substance of heredity from germ-cell to germ- 
cell of parent and offspring; it supposes that in 
each successive generation the germ-cells are zholly 
supplied with their germinal material from somatic- 
cells of each individual organism. Or, adopting our 
previous terminology, the three theories may be 
ranked thus. 

The particulate elements of heredity all proceed 
centripetally from somatic-cells to germ-cells (gem- 
mules): the inheritance of acquired characters is 
therefore habitual. 

These particulate elements proceed for the most 
part, though not exclusively, from germ-cells to 
somatic-cells (stirp): the inheritance of acquired 
characters is therefore but occasional. 

The elements in question proceed exclusively in 
the centrifugal direction last mentioned (germ-plasm): 
the inheritance of acquired characters is therefore 
impossible '. 

‘ Professor Weismann still maintains that there is a further important 
distinction between the theories of pangenesis and germ-plasm, in that 
the one is pre-formative while the other is epigenetic. But I am still 


unable to perceive that such is the case. He argues, indeed, that his 
new doctrine of determinants emphasizes this distinction: the argument, 


134 An Examination of Wetsmannism. 


Such being the fundamental points of difference 
between these three theories of heredity, we have now 
to consider more particularly those which obtain 
between Galton’s and Weismann’s. 

The general doctrine of gemmules (i.e. somatic- 
cell-germs) is accepted by Galton; but instead of 
supposing, as Darwin supposed, that these minute 
bodies freely circulate through all the body tissues, 
so that some of them are absorbed from all the 
somatic-cells by the germ-cells, and there constitute 
the entire mass of hereditary material out of which 
the offspring will afterwards be formed, Galton sup- 
poses that gemmules circulate with comparative diff- 
culty, and that only comparatively few of them gain 
access to the germ-cells in each generation. Hence, 
characters acquired in the individual lifetime are 
much less heritable than those which are called con- 
genital. For congenital characters are due to the 
“continuity ” of stirp through numberless genera- 
tions in the phylogeny of the organism ; hence such 
characters are represented by a vastly greater number 
of equivalent hereditary elements. Weismann, on the 
other hand, rejects the doctrine of gemmules zz Zo/o. 

Again, according to Galton’s view, “individual 


however, appears to me radically unsound. For instance, he says, “ The 
hereditary continuation in each part is pre-determined in each part 
from the germ onwards. The right and left ears could not possibly 
resemble each other, if the relative strength of the hereditary tendencies 
on both sides were not pre-determined for all parts of the child by the 
nature of the paternal and maternal idants.” Very well. But, if so, the 
theory of determinants is just as much pre-formative as is that of 
gemmules. Or, conversely, the latter is quite as epigenetic as the former. 
Both are alike determinative, while neither supposes that the determina- 
tion is due to a pre-formed miniature of the future child in the fertilized 
egg of its mother; but to a particulate v~efresentation in the latter of 
every heritable part of the former. 


Wetsmannism up to date (1893). 135 


[congenital] variation depends upon two factors; 
the one is the variability of the germ! and of its 
progeny ; the other is that of all kinds of external 
circumstances, in determining which out of many 
competing germs, of nearly equal suitability, shall be 
the one that becomes developed. The variability 
of germs under changed conditions, and that of their 
progeny, may be small, but it is indubitable ; absolute 
uniformity being scarcely conceivable in the condition 
and growth, and, therefore, in the reproduction of any 
organism. The law of heredity goes no further than 
to say, that like tends to produce like ; the tendency 
may be very strong, but it cannot be absolute *.” 
Here, of course, there is a wide difference between 
stirp and germ-plasm. For while Galton does not 
entertain amphimixis among the “factors” of con- 
senital variation, Weismann, as we are now well 
aware, has hitherto regarded it as the sole cause 
of such variation. Nevertheless, as we shall presently 
find, Weismann has now greatly modified his views 
upon this point, and does entertain, in 7e Germ-plasm, 
both the “ factors” mentioned by Galton. Hence, the 
difference between the two theories in question with 
regard to this matter is not nearly so wide as it was 
prior to the publication of Weismann’s last work. 
The next most important point of difference 
between the theories of stirp and germ-plasm has 
reference to the mechanism of ontogeny. According 
to Galton, this is simply a struggle between all the 


1 By “germ” Galton means a carrier of heredity, which is capable 
of self-multiplication. In these fundamental respects, therefore, it is 
equivalent to a ‘‘gemmule” on the one hand and a “‘ determinant” on 
the other. The three terms are so far synonymous, 

2 Loc. cit., p. 338. 


136 An Examination of Wetsmannism. 


carriers of heredity composing the stirp of a fertilized 
ovum. It is not, however, a struggle for existence, 
but what may be called a struggle for development. 
In the fertilized ovum all the carriers of heredity are, 
to begin with, in a “latent” condition ; but of this 
enormous multitude of “ germs” or “gemmules,” only 
a very small proportional number are destined to 
become “ patent ”—i. e., developed into the tissue-cells 
composing the new organism. The vast majority 
of the gemmules, or those which fail to be thus de- 
veloped, go to constitute the stirp of the new organism 
when this has been formed by the development of the 
comparatively few successful gemmules. Thus much 
understood, the following quotation will be fully 
intelligible. 


My argument is this: Of the two groups of germs, the 
one consisting of those that succeed in becoming developed 
and in forming the bodily structure, and the other consisting of 
those that remain continually latent, the latent vastly prepon- 
derates in number. We should expect the latent germs to 
exercise a corresponding predominance in matters of heredity, 
unless it can be shown that, on the whole, the germ that is 
developed into a cell becomes thereby more fertile than if it had 
remained latent. But the evidence points the other way. It 
appears both that the period of fertility: is shorter, and the 
fecundity even during that period is less in the germ that 
becomes developed into a cell, than they are in the germ that 
remains latent. Much less then would the entire bodily 
structure, which consists of a relatively small number of these 
comparatively sterile units, successfully compete in matters of 
heredity with the total effect of the much more numerous and 
more prolific units which are in a latent form’. 


Thus, Galton’s theory of the mechanism of onto- 


A Lee tit. De 320: 


Wetsmannism up to date (1893). 137 


geny is a theory of struggle; and this constitutes 
a point of difference on which Weismann lays much 
stress in his latest work. For, as we know, Weismann 
regards the mechanism of ontogeny as characterized 
by a peaceful succession of “ stages,” which are “ pre- 
determined from the germ onwards”’; and in his latest 
work this idea of orderly sequence has been further 
elaborated in his doctrine of “determinants.” In 
short, to adopt their own metaphors, while Galton 
tells us that the mechanism of ontogeny is like that 
of a political election, where rival candidates compete 
to “represent ” the nation (stirp) in Parliament (indi- 
vidual organism) ; Weismann likens it to the mechan- 
ism of a well-drilled army, where ultimate carriers 
_of heredity (privates) are banded together in com- 
panies, regiments, battalions, &c., under the command 
of corresponding officers (determinants). 

Lastly, there is yet one further point of difference 
between stirp and germ-plasm, which is thus stated 
by Weismann :— 


Galton’s idea is only conceivable on the presupposition of the 
occurrence Of sexual reproduction, while the theory of the 
continuity of the germ-plasm is entirely independent of any 
assumption as to whether each primary constituent is present in 
the germ szzgly or in numbers. According to my idea, the 
active and the reserve germ-plasm contain precisely similar 
primary constituents, gemmules, or determinants; and on this 
the resemblance of a child to its parent depends. The theory 
of the continuity of the germ-plasm, as I understand it, is not 
based on the fact that each “‘gemmule” necessary for the con- 
struction of the soma is present many times only, so that a residue 
remains from which the germ-cells of the next generation may be 
formed : it is founded on the view of the existence of a special 
adaptation, which is inevitable in the case of multicellular organ- 
isms, and which consists in the germ-plasm of the fertilized 


138 An Examination of Wetsmannism. 


egg-cell becoming doubled primarily, one of the resulting portions 
being reserved for the formation of germ-cells’. 


These being the main points of difference between 
the theories of stirp and of germ-plasm to which 
Professor Weismann has alluded, I will now proceed to 
consider them separately, in reverse order to that in 
which they have been here stated. 

The point of difference last mentioned need not 
detain us long, because it seems to me one of very 
little importance. “ Whether each primary constituent 
is present in the germ singly or in numbers” cannot 
ereatly signify, so long as both theories agree that, 
sooner or latter, they must be present plurally. 
Galton supposes them to be thus present from the 
first (i.e. in the unfertilized ovum), while Weismann 
supposes them to be so only as a result of their self- 
multiplication at a somewhat later stage (i.e. in 
the segmenting ovum, and onwards throughout the 
procreative life of the individual). Doubtless Weis- 
mann does not suppose that they ever become so 
numerous as Galton imagines; but the whole question 
is so highly speculative that I do not see how any 
useful purpose can be served by debating it. Nor do 
I see why Weismann should conclude that “ Galton’s 
idea is only conceivable on the presupposition of the 
occurrence of sexual reproduction.” It is true that 
Galton has discussed exclusively the case of sexual 
reproduction; but I cannot perceive that any of his 
ideas are inapplicable to a-sexual. 

Touching the question whether the phenomena of 
ontogeny had best be ascribed to a competition 
among a vast number of “germs,” or to a strictly 


1 The Germ-plasm, pp. 199, 220. 


Weismannism up to date (1893). 139 


ordered evolution of a comparatively small number 
of “determinants,” a considerable array of arguments 
might be adduced in support of either view. Thus, 
Galton might well maintain that his interpretation 
of the observable facts is most in accordance with the 
eeneral analogies supplied by organic nature as a 
whole. The ancient aphorism of Heraclitus, “Struggle 
is the father, king, and lord of all things,” has been in 
large measure justified by Darwin and his followers, 
at any rate within the range of biology. Not only 
have we the “struggle for existence” where “the 
origin of species” is concerned; but Roux has well 
argued, in his remarkable work on Der Kampf der 
Theile 1m Organismus, that the principle of “struggle” 
is concerned to an equally important extent as 
between all the constituent parts of the same indi- 
vidual. But if this is so—if every tissue-cell of the 
organism owes its maintenance to success in a general 
contest for nutriment, &c.,—do we not find at least 
a probability that it owes its origin as a visible 
cell to a similar success in a similarly general contest 
among the invisible elements from which tissue-cells 
are developed? Nay, does it not seem well nigh 
incredible that when this selection-principle is seen to 
be the governing cause of evolution everywhere else, 
it should cease to play any part at all just at the 
place where we are unable to see what is going on? 
As we are agreed that this “father of all things ” 
is of prime importance in phylogeny—to say nothing 
of physiology, psychology, and sociology,— must we 
not deem it absurd to suppose that it is supplanted 
in ontogeny by the opposite principle of absolute 
peace P 


140 An Examination of Wersmannism. 


On the other hand, Weismann adduces many 
forcible considerations per contra; so that, in the 
result, I deem it best to dispose of the question with 
two general remarks, The first is, that the rival views 
are not necessarily incompatible. Each may present 
one aspect of the truth. Weismann’s doctrine of 
determinants may be—and, to the best of my judge- 
ment, must be—sound ; but this does not hinder that 
Galton’s doctrine of struggling “germs” may be so 
likewise. For, as we have already seen, these germs 
present the same compound character which belong 
to determinants ; in fact I do not suppose that Galton 
would object to identifying them with determinants. 
On the other hand, I do not see why Weismann 
should object to supposing that similar determinants 
compete among themselves for ontogenetic develop- 
ment. Indeed, he has already argued, in his 
suggestive theory of “germ-tracts,’ that it is usually 
only one among a number of similar determinants 
which does succeed in achieving such development— 
or, as he expresses it, which “‘ becomes active.” But 
what is it that causes this activity? Surely it must be 
some superiority on the part of the active determinant 
over its passive companions. And, if so, it is the 
selection-principle that is here at work. In fact, he 
has himself laid no small stress on what he calls “the 
struggle of the determinants of the two parents in 
ontogeny,” and has even supplied a long section or 
“the Struggle of the Ids in Ontogeny.” Therefore 
I do not see why he should so emphatically dissent 
from Galton’s view upon this matter as he does 
in his work on The Germ-plasm}. 


* pp: 72-4. 


Weismannism up to date (1893). 141 


My second remark is a brief one—viz., that the 
whole question is of so very speculative a character, 
that I cannot see the smallest use in debating it. 

The only remaining point of difference between 
strip and germ-plasm is the one referring to stability. 
Needless to say, Galton is at one with Weismann in 
recognizing a high degree of stability on the part of 
the substance of heredity ; but the agreement extends 
only so far as is necessitated by the facts of atavism, 
&c. Indeed, he does not even mention—although he 
perhaps implies—what Weismann has called amphi- 
mixis as among the factors of individual congenital 
variation. Weismann, on the other hand, has hitherto 
regarded amphimixis as the sole cause of all such 
variations. But, as we shall presently find, in his 
recent work on The Germ-plasm he has now greatly 
modified his views upon this subject, and, in fully 
recognizing the “factors” of variability to which 
Galton alludes, has correspondingly lessened the 
difference between germ-plasm and stirp. But this is 
a point which can be better dealt with when we come 
to consider the important modifications which in this 
respect the theory of germ-piasm has undergone. 


The only other matter which has to be mentioned 
in connexion with Weismann’s theory of heredity is, 
that in Zhe Germ-plasmhe has for the first time given 
us his views upon the influence of a previous sire on 
the progeny of a subsequent one by the same dam. 
The phenomena in question, which I have already 
detailed in pp. 77-9, 110, he designates by the term 
“telegony.” The analogous phenomena in plants he 
calls, following Focke, “ xenia.” 


142 An Examination of Wersmannism. 


With regard to telegony, he adopts, almost pre- 
cisely, the position which I surmised that he would. 
That is to say, he first disputes the alleged facts, and 
then argues that, even if they be facts, they admit of 
being explained on the theory of germ-plasm by 
supposing that some of the germ-plasm from the 
first sire penetrates the unripe ova which are after- 
wards fertilized by the second?. The only difference 
between his views and my own upon this matter is, 
therefore, as follows. 

Supposing that the phenomena alleged ever occur 
in fact, I have said that the only way of explaining 
them would seem to be, “ that the life of ‘germ-plasm’ 
is not conterminous with that of the spermatozoa which 
convey it, and hence that, if the carriers of heredity, 
after the disintegration of their containing sperma- 
tozoa, should ever penetrate an unripe ovum, the 
germ-plasm thus introduced might remain dormant 
in the ovum until the latter becomes mature, and is 
then fertilized by another sire. In this way it is con- 
ceivable that the hitherto dormant germ-plasm of the 
previous sire might exercise some influence on the 
ontogeny of the embryo *.” 

Now, this is substantially the position which Weis- 
mann takes up: only instead of supposing that it is 
the “carriers of heredity” of the first sire which gain 
access to the unripe ovum “after the disintegration 
of their containing spermatozoa,’ he supposes that it 
is one of the spermatozoa which does so before its 
disintegration has commenced. Of course there is 
here no difference in principle, but only a question 
touching the mode in which the access is presumably 


1 The Germ-plasm, pp. 383-386. 2 Quoted from above, p. 78. 


Wetsmannism up to date (1893). 143 


effected. But, as regards this question, I retain my 
original opinion. For, while I can see no theoretical 
difficulty in supposing that “the carriers of heredity,” 
when set free by the disintegration of their containing 
spermatozoa, may reach the unripe ova while still 
embedded in the depths of the ovary, I do see a 
difficulty, amounting almost to a physiological im- 
possibility, in supposing that a whole spermatozoon 
can perform such a feat. From all that we know 
about the powers and functions of spermatozoa in the 
vertebrata, it appears simply absurd to imagine that 
these bodies are able to penetrate the dense coating of 
an ovary, and then delve their way through the stroma. 
There is, indeed, a remarkable investigation which 
was published a year or two ago by Mr. Whitman! 
which appears to prove that in certain leeches the male 
injects his seminal fluid into any part of the body of 
the female, and that the spermatozoa then reach the 
ova by wandering about her general tissues until some 
of them happen to hit upon her ovary. But in this 
case the spermatozoa are specially adapted to perform 
such acts of penetration—being spear-like bodies 
provided with a sharp point. Hence, if Weismann 
should quote this instance, it would not tend to 
support his view, seeing that the spermatozoa of 
mammals do not exhibit any such specializations of 
structure ; and therefore, before any one of them can 
effect fertilization, must wait for the ovum to mature, 
reach the surface of the ovary, and rupture its follicle. 

But, as already observed, it does not signify, so 
far as we are here concerned with the matter, in what 
precise manner the telegonous influence may be 


' Morph. Journal, vol. ii. 


144 An Examination of Wetsmannism. 


supposed to be exercised—-provided that it may be 
so directly, and not necessarily through first having 
to influence the whole material organism. Therefore 
I quite agree with Weismann that the facts—sup- 
posing them to be facts—are quite as explicable by 
the theory of germ-plasm-as by that of pangenesis !. 
Again, with respect to xenia, Weismann writes :— 
As such eminent botanists as Focke, and more recently 
De Vries, have expressed much doubt with regard to these obser- 
vations—or rather interpretations—we must wait until these 
cases have been critically re-investigated before attempting to 
account for them theoretically. The chief difficulty we should 
meet with in any such explanation would be due to the fact that 
we are here concerned with the influence of the germ-f/asm of the 
sperm-cell on a tissue of another plant which only constitutes 
a part of this plant. It would thus be necessary to assume that 
all the determinants of this germ-plasm are not active, and that 
only those take effect which determine the nature of the fruit. 


Now, it does not appear that De Vries has looked 
into the matter on his own account, as he merely 
refers to what Focke has said. And this amounts 
merely to showing the dubious character of some 
half-dozen cases which Focke gives as those which 
alone have fallen within his cognizance. Why he 
does not mention any of the numerous cases which 
are quoted by Darwin, I do not understand. Nor 
can I understand why he does not consider what seem 
to be the particularly conclusive facts given on 
p. 80,—i.e, where xenia appears to constitute “a 
needful preliminary to fertilization.” But the whole 
matter is one for botanists to deal with, and if any 
doubt attaches to it, at least the grounds of such 
doubt should be fully stated. Still more, in my 

' See Appendix II. 


Wersmannism up to date (1893). 145 


opinion, should the matter be freed from any such 
doubt. The question—if there be a question—is one 
of great interest from a merely physiological point 
of view, while in relation to the fundamental 
problems of heredity its importance is immense. 
Surely, then, any competent botanist who disputes 
the facts ought to test them by way of experiment. 
But, be this as it may, I must call prominent 
attention to the following very remarkable words 
wherewith Weismann concludes the passage above 
quoted. For he there says, that even supposing there 
were no doubt as to the facts or their interpretation, 
“the chief difficulty’ which they would oppose to 
the theory of germ-plasm would be, “that we are 
here concerned with the influence of the germ-plasm 
of the sperm-cell on a tissue of another plant which 
only constitutes a part of this plant.” In other words, 
Weismann now freely entertains the possibility of a 
direct action of germ plasm n the somatic tissues, 
even though these belong to another individual! 
Thus he now concedes the only point for the 
establishment of which I adduced the phenomena 
of xenia, in Chapter III: the whole of one side 
of that “reciprocal action between the sphere of 
germinal-substance and the sphere of body-sub- 
stance,” which I contended for on pp. 76-85, is now 
conceded ; and although it is the less important 
side, its surrender goes far to weaken the doctrine 
of a perpetual isolation of germinal-substance to 
a “sphere” of its own. If we suppose that the 
germinal substance of one organism may thus 
directly act upon the somatic tissues of another, 
and that changed conditions of life are able to 
L 


146 An Lxamination of Wetsmannism. 


produce simultaneously an acquired character in 
the soma and a precisely identical character as 
congenital in the germ (pp. 129-30), we are plainly 
. inviting ourselves to abandon the complex explana- 
tien of living material in “two kinds,’ where one is 
capable in all sorts of ways of communicating with 
the other, while the possibility of any reciprocal action 
is excluded. For the simpler hypothesis of living 
material as all of one kind encounters no such 
antinomies. So long as one kind of this material 
was supposed to be as distinct from the other asa 
parasite is distinct from its host, there was not so 
much to choose between the theory of germ-plasm 
and that of gemmules in this respect of simplicity. 
But the more that the former theory has had to be 
adjusted to facts, the greater has its complexity 
become, until now its own author is obliged to make 
so many additional assumptions for the purpose 
of maintaining it, that we begin to wonder how long 
it can continue to support the weight of its accuma- 
lating difficulties. 


So much for the main modifications which have 
this year been made in Weismann’s postulate of the 
perpetual continuity of germ-plasm. We must next 
consider the changes which he has effected in his 
companion postulate of the absolute stability of 
germ-plasm. 


Wetsmannism up to date (oOsjey 147 


Wetsmanun’s Theory of Evolution (1893). 


Of far more importance than any of the alterations 
which Professor Weismann has recently made in his 
theory of heredity, are those whereby he has modi- 
fied his sequent theory of evolution. For while, 
as we have just seen, his work on 7he Germ-plasm 
leaves the former theory substantially unaltered — 
although largely added to in matters of detail,—it 
so profoundly modifies the latter that careful readers 
will find no small difficulty in ascertaining how much 
of it has been allowed to remain. I will consider 
only the main modifications, and these I will take 
separately. 


It will be remembered that one distinctive feature 
in Weismann’s theory of evolution has hitherto been, 
that the unicellular organisms differ from the multi- 
cellular in the following important particulars. 

1. There being no division in unicellular organisms 
between germ-cells and somatic-cells, there is no 
possibility in them of the occurrence of amphimixis. 

2. Consequently, there is no possibility in them of 
congenital variations, in the sense that these occur 
in multicellular organisms. 

3. Hence the only causes of individual variation 
and of the origin of species in the unicellular organ- 
isms are the Lamarckian factors, just as in the multi- 
cellular the only cause of these things is natural 
selection. 

4. Hence, also, the unicellular organisms are poten- 

L 2 


148 An Examination of Wetsmannism. 


tially immortal, while the multicellular have acquired 
mortality for certain adaptive reasons. 

But now, with the exception of No. 4, all these 
positions have been abandoned. For, chiefly on 
account of the beautiful researches of Maupas, Weis- 
mann has come to perceive that no real distinction 
can be drawn between an act of sexual union in 
the multicellular organisms, and an act of conjuga- 
tion in the unicellular. Amphimixis, therefore, is 
now held by him to occur equally in both these 
divisions of organic nature, with the consequence 
that the Protozoa and Protophyta owe their indi- 
vidual variations, and therefore the origin of their 
innumerable species, as exclusively to the action 
of natural selection as is the case with the Metazoa 
and Metaphyta. In fact, the term “amphimixis”’ has 
been coined in express relation to these very points. 

It will be seen, however, that this important change 
of view merely postpones the question as to the 
origin of amphimixis, if the object of this process be 
that which Weismann supposes—viz., the providing of 
material in the way of congenital variations on which 
natural selection can act. Therefore he is obliged 
to assume that there now are, or once have been, 
organisms of a less organized character than even the 
lowest of the unicellular forms—organsims, that is 
to say, which possess no nucleus, but are wholly 
composed of undifferentiated bioplasm. These most 
primitive organisms it must have been that were not 
subject to any process of natural selection, but, in virtue 
of an exclusive action of the Lamarckian factors upon 
their protoplasmic substance, gave rise to individual 
variations which subsequently gave rise to a unicellular 


Wersmannism up to date (1893). 149 


progeny—when the process of natural selection was 
immediately inaugurated, and thereafter entirely 
superseded the Lamarckian factors. Or, to state the 
matter in Weismann’s own words :— 

My earlier views on unicellular organisms as the source of 
individual differences, in the sense that each change called forth 
in them by external influences, or by use and disuse, was 
supposed to be hereditary, must therefore be dismissed to some 
stage less distant from the origin of life. I now believe that 
such reactions under external influences can only obtain in the 
lowest organisms which are without any distinction between 
nucleus and cell-body. All variations which have arisen in 
them, by the operation of any causes whatever, must be in- 
herited, and their hereditary individual variability is due to the 
direct influence of the external world..... If I am correct in 
my view of the meaning of conjugation as a method of amphi- 
mixis, we must believe that all unicellular organisms possess it, 
and that it will be found in numerous low organisms, in which 
it has not yet been observed '. 

It is not very clear, at first sight, how Professor 
Weismann, after having thus abandoned the _pro- 
positions 1, 2,and 3, as above stated, manages to retain 
his former view as given in No. 4. Nevertheless he 
does so, by representing that a unicellular organism, 
even though it present such a considerable degree of 
organization as we meet with in the higher Protozoa, 
still resembles a germ-cell of a multicellular organism, 
in that it consists of all the essential constituents of 
a germ-cell, including germ-plasm in its nucleus. And 
inasmuch as agerm-cell is potentially immortal, so it 
must be with a unicellullar organism; in the one 
case, as in the other, the design of the structure is 
that its contained germ-plasm shall fuse with the germ- 
plasm contained in the nucleus of another individual 

' Essays on Heredity, vol. ii. pp. 193-4. 


150 An Examination of Wersmannism. 


cell, when the life of both will be preserved. For 
my own part, however, I cannot see that in either 
case the ce//, as distinguished from its contained germ- 
plasm, is thus, shown to be potentially immortal. On 
the contrary, it appears to me a mere accident of 
the case that in a unicellular organism the immortal 
substance (germ-plasm) is contained in a single cell, 
which is at the same time a free cell, and, as such, is 
denominated an “organism.” We might just as well 
call a germ-cell an “ organism,’ whether as an ovum 
it happens to be embedded in a mass of somatic-cells, 
or as a locomotive spermatozoon it happens to be 
free. In fact Weismann himself appears to recognize 
this. But, if so, it is surely a distinction without 
a difference to say that unicellular organisms are 
immortal, while multicellular are mortal. For in 
neither case is the organism immortal, while in both 
cases it is the germ-plasm (i.e., the substance of heredity) 
that is so. Where the cell containing the germ-plasm 
happens to be a free cell, it is called an “organism” ; 
but whether it be a germ-cell or a protozoan, it alike 
ceases to be a cell when it has given origin to a 
multitude of other cells, whether these happen to be 
other germ-cells (A/zs somatic-cells) or other proto- 
zoan cells. In short, gwd cell, all cells are mortal: 
it is only the substance of heredity which some cells 
contain that can be said, in any sense of the term, to 
be immortal. [For the immortality in question does 
not belong to unicellular organisms as such, but to the 
germ-plasm which they contain. And from this it 
follows that, as the immortality of germ-plasm is 
one and the same thing as the continuity of germ- 
plasm, by alleging an immortality as belonging to 


Wersmannism up to date (1893). 151 


the unicellular organisms, Weismann is merely re- 
stating his fundamental postulate. Hence, also, he 
is but denying, in a somewhat round-about way, the 
occurrence of spontaneous generation. 

I conclude, therefore, that his sole remaining 
distinction between the unicellular and the multi- 
cellular organisms is but illusory, or unreal. And, 
with regard to the great change which he has thus 
effected in his system by expressly abolishing all the 
other distinctions, I have only to say that in my 
opinion he has thereby greatly improved his system. 
For he has thus relieved it of all the formidable 
difficulties which he had needlessly created for him- 
self, and which I have already enumerated in the 
foregoing pages (88-89). In his ever-shifting drama 
of evolution the unicellular organisms have left the 
stage en masse, and, so far as they are concerned, 
we are all as we were before the curtain rose. 


But of even more importance than this funda- 
mental change of view with regard to the unicellular 
organisms, is a further and no less fundamental 
change with regard to the multicellular. That such 
is the case will immediately become apparent by 
a simple statement of the fact, that Weismann has 
now expressly surrendered his postulate of the abso- 
lute stability of germ-plasm! 

We have already seen that, even in the first volume 
of his £ssays, there were some passages which gave 
an uncertain sound with regard to this matter. But 
as they seemed attributable to mere carelessness on 
the part of their author, after quoting a sample 
of them, I showed it was necessary to ignore such 


152 An Examination of Wersmannism., 


inconsistent utterances—necessary, that is, for the 
purpose of examining the theory of germ-plasm as 
even so much as a logically coherent system of ideas}. 
For we have seen that if any doubt were to be 
entertained touching the absolute stability of germ- 
plasm “since the first origin of sexual propagation,” 
a corresponding measure of doubt would be cast on 
Weismann’s theory of congenital variation as solely 
due to: amphimixis, with the result that his whole 
theory of evolution would be similarly rendered 
dubious. Since then, however, he has gone very 
much further in this direction. First, in reply to 
Professor Vines he says (1890) :— 


I am at present inclined to believe that Professor Vines is 
correct in questioning whether sexual reproduction is the only 
factor which maintains Metazoa and Metaphyta in a state of 
variability. I could have pointed out in the English edition 
of my “ Essays” that my views on this point had altered since 
their publication ; my friend Professor de Bary, too early lost to 
science, had already called my attention to those parthenogenetic 
Fungi which Professor Vines justly cites against my views; but 
I desired, on grounds already mentioned, to undertake no altera- 
tion in the essays ”. 


Next, in his essay on Amphimixis (1892), there are 
several passages to somewhat the same effect ; while, 
lastly, in his Germ-plasm (1893), the fundamental 
postulate in question is, as I have said, expressly 
surrendered. For example, we have in the following 
words the final conclusions of his recent arguments. 
Speaking of amphimixis, he says :— 

It ts not the primary cause of hereditary variation. By its 
means those specific variations which already exist in a species 


* See above, pp. 63-07. 2 Nature, vol. xli. p. 322. 


Wersmannism up to date (1893). 153 


may continually be blended in a fresh manner, but it is incap- 
able of giving rise to new variations, even though it often 
appears to doso.... Zhe cause of hereditary variation must lte 
deeper than this. It must be due to the direct effects of external 
influences on the biophores and determinants '. 


These quotations are enough to show that Weis- 
mann has now abandoned his original theory of 
congenital variations being exclusively due to amphi- 
mixis, and adopts in its stead the precisely opposite 
view—viz., that the origin of all such variations must 
be ascribed to the direct influence of causes acting on 
germ-plasm from without. Up to the present year 
the very essence of the whole Weismannian theory 
of evolution has been that, owing to the stability 
of germ-plasm since the first origin of sexual pro- 
pagation, “the origin of hereditary individual varia- 
tions cannot indeed be found in the higher organisms, 
the Metazoa and Metaphyta; but is to be sought 
for in the lowest—the unicellular organisms,” because 
“the formation of new species, which among the 
lower Protozoa could be achieved without amphigony, 
could only be attained by means of this process in 
the Metazoa and Metaphyta. It was only in this 
way that hereditary individual differences could arise 
and persist *.” 

But about the beginning of the present year we 
have this fundamental doctrine directly contradicted 
in such words as :— 


The origin of a variation is equally independent of selection 
and amphimixis, and is due to the constant occurrence of slight 
inequalities of nutrition in the germ-plasm *. 


1 The Germ-plasm, pp. 414-415. Italics Weismann’s, 
ST Rsays), VOLnI Degas * The Germ-plasm, p. 431. 


/ 


154 An Examination of Wersmannism. 


This complete reversal of his previous doctrine 
brings Weismann into line with Darwin, who long 
ago gave very good reasons for the following con- 
clusion :-— 


Those authors who, like Pallas, attribute all variability to the 
crossing either of distinct races, or to distinct individuals belong- 
ing to the same race but somewhat different from each other, 
are in error; as are those authors who attribute all variability 
to the mere act of sexual union [Lamphimixis|'. 


And again :— 


These several considerations alone render it probable that 
variability of every kind is directly or indirectly caused by 
changed conditions of life. Or, to put it under another point 
of view, if it were possible to expose all the individuals of a 
species during many generations to absolutely uniform con- 
ditions of life, there would be no variability 2. 


Hence, Darwin was disposed to find the main, 
if not the only, causes of congenital variations in 
circumstances depending for their efficacy on the 
instability of what Weismann calls germ-plasm. And 
the noteworthy fact is, that Weismann has now 
adopted this view, to the destruction of his originally 
fundamental postulate touching the stadz/ity of germ- 
plasm since the first origin of sexual propagation. 


By such a right-about-face manceuvre, Weismann 
has placed his critics in a somewhat difficult position. 
For, in the first place, it is only towards the close 
of Zhe Germ-plasm that the manceuvre is executed, 
and then only in a few sentences such as I have just 
quoted — italicized, it is true, but otherwise so slightly 


1 Var tation &c., vol. i. p. 398. 2 Jbid., vol. ii. p. 242. 


Wetsmannism up to date (1893). 155 


emphasized that, as Professor Hartog has observed, 
no one of his reviewers has noticed it'. In the 
second place, he nowhere expressly recognizes the 
effects upon his theory of evolution, which necessarily 
follow from the change. And, lastly, the manner in 
which he endeavours to underpin that theory after 
having thus removed its logical foundation in his 
former postulate of the absolute stability of germ- 
plasm, is so peculiar that it is hard to epitomize his 
casoning with due regard to brevity. 

Speaking for myself, I can only say that my first 
impulse, after reading the sentences above quoted, 
was to cancel the whole of Chapter IV, as well as all 
those parts of Chapters I and III where the Weis- 
mannian theory of evolution is alluded to; and then 
to start anew with a bare statement that this theory 
had now been wholly discarded by its author. But 
after due consideration it seemed desirable to leave 
the criticism as it was originally written, not only on 
account of the reasons already stated in the Preface, 
but still more because I found it would be impractic- 
able to start a new criticism of the greatly modified 
theory of evolution without introducing many and 


1 Nature, May 11, pp. 28-29.—In 1891-2 Professor Hartog furnished 
a criticism of Weismann’s theory of Heredity (ature, vol. 44. p. 613, 
and Contemporary Keview, July, 1892). Although disputed at the time 
by some of Weismann’s followers in England, this criticism was one of 
unquestionable cogency, and has now been recognized as such by 
Weismann himself (7he Germ-flasm, pp. 434-5). The main point of 
the criticism had been missed by previous critics of Weismann, and 
consisted in revealing an important “ difficulty ” inherent in the structure 
of the theory itself. How far this criticism had the effect of causing 
Professor Weismann to abandon his theory of variation being ex- 
clusively due to amphimixis, as Professor Hartog appears to think 
(Nature, May 11, 1893, p. 28), is immaterial. But it must be observed 
that as far back as February, 1890, Professor Weismann in his answer to 
Professor Vines’ criticism wrote the passage already quoted on page 152, 


156 An Examination of Weismannism. 


lengthy parts of the old one, for the purpose of 
showing how the most recent theory had been arrived 
at. Hence, seeing that my previous criticism was 
far from having been rendered obsolete by the large 
changes which had taken place in Weismann’s system 
of theories, I concluded that it was best to retain 
what I had written, and add the present paragraphs 
for the purpose of dealing exclusively with the 
changes in question. 

In now proceeding to do this, I think it is needless 
to occupy space by giving the reasons which have 
caused Weismann thus to abandon his doctrine of the 
universal stability of germ-plasm since the first origin 
of sexual propagation, and to substitute the precisely 
opposite doctrine of its universal instability. It is 
enough to say that these reasons all arise by way 
of logical necessity from the further working out in 
The Germ-plasm of his theory of heredity—or, more 
correctly, from the additions which he has there made 
to his previous views on the mechanism of heredity. 
Thus he has reversed his former doctrine touching 
the absolute stability of germ-plasm, not so much 
on account of any of the general considerations or 
particular facts which I have adduced against it in 
Chapter IV, as because it would not tally with the 
recent additions which he has made to other parts 
of his system. Any one who cares to follow this 
matter will find the reasons in question fully and 
lucidly stated in Chapter XIV of The Germ-plasm'. 

1 Tt is almost needless to say that no fault is to be found with 
Weismann for having thus reversed his opinion touching one of his 
fundamental postulates. Consistency is no merit in a man of science; 


and least of all where matters of such high speculation are concerned. 
I think, however, that it is open to question whether an author of any 


Wetrsmannism up to date (1893). 157 


It is of more importance to consider the means 
whereby Weismann seeks to save his theory of evo- 
lution after he has thus removed its foundation in his 
former postulate of the absolute stability of germ- 
plasm. As far as I can understand, he seeks to do so 
as follows. 

In the first place, it must be noted that after 
his changes of view with regard to polar bodies, 
unicellular organisms, and the significance of sexual 
reproduction, nothing remains of his original theory 
of evolution save what he can manage to retain of his 
original theory of variation as due to amphimixis. 
But, as we have just seen, he has surrendered this 
latter theory also. ‘Therefore, at first sight it appears 
that no part of the former can possibly remain. 
Beginning at the apex, he has removed, stone by 
stone, his doctrine of descent, and, on arriving at 
its fundamental postulate—the absolute stability of 
cerm-plasm—simply turns it upside down. Surely, 
therefore, it may be thought, there is here as complete 
a destruction as well could be of all this side of 
Weismann’s system. Such, however, he endeavours 
to show is not the case. He regards it as still possible 
to retain so much of his theory of descent as is 
presented by what he can save of his theory of vari- 
ation, thus :— 

Although he now represents that the zzstadzlity of 


kind should suffer an elaborate system of theories to be published and 
translated, at the very time when he is himself engaged in producing 
another work showing the untenable character of their basal premises. 
At any rate, it would have saved his English readers no small trouble 
and confusion, if Weismann had added notes to the translations of his 
essays on Lolar Bodies, on The Significance of Sexual Reproduction, 
and on Amphimixts, to the effect that he had abandoned some of 
their most distinctive features before the translations liad gone to press. 


158 An Examination of Wetsmannism. 


germ-plasm is such that in zo case can amphimixis . 
have had anything to do with the orzgzxz of congenital 
variations, he continues to regard the szadzlity of 
germ-plasm sufficiently great to necessitate, in ad/ 
cases, the occurrence of amphimixis in order to 
promote the development of congenital variations. In 
other words, notwithstanding that he now thinks all 
congenital variations must be begun by external 
conditions acting directly on an unstable germ-plasm, 
he also thinks that the amount of variation thus 
produced is likely to be exceedingly minute, and 
must therefore be increased by subsequent amphi- 
mixis in order to fall within the range of natural 
selection. So that, although powerless to initiate 
congenital variation, amphimixis must still play an 
indispensable part in the process of evolution, as in 
all cases a necessary condition to the occurrence of 
natural selection. External conditions first cause 
slight changes in the determinants of a species; but 
these are so slight that they have to be augmented by 
amphimixis before they constitute material on which 
natural selection can act, and hence before they can 
become of any significance either in ontogeny or 
phylogeny. 

Such, I take it, is what Professor Weismann would 
now have us to understand; for otherwise I should 
have expected from him as frank a surrender of his 
theory of evolution (or the remnant thereof in his 
theory of variation) as he has made of its funda- 
mental postulate. But, if such is his meaning, I may 
mention the reasons which appear to me to render 
it nugatory. 

In the first place, it is evident that in thus 


Wersmannism up to date (1893). 159 


minimizing the possible range of congenital variation 
due to the action of external conditions on a non- 
absolutely stable substance of heredity, Weismann 
is making a wholly gratuitous assumption, for the 
sole purpose of saving what remains of his theory 
of evolution—i.e., the doctrine of the immense im- 
portance of amphimixis> 

We have already seen in the foregoing chapter, 
that his original assumption of the adsolute stability 
of germ-plasm was a gratuitous one, made for the 
purpose of supplying a foundation for constructing 
his theory of evolution. But still more gratuitous 
is the assumption which he has now substituted, for 
the purpose of saving as much of this theory as 
is left—the assumption, namely, that germ-plasm, 
although universally unstable, nevertheless everywhere 
presents only a certain low degree of instability, 
which serves to accommodate his modified theory 
of heredity on the one hand, and all that is possible 
of his previous theory of evolution on the other. His 
original assumption, untenable though it was, fur- 
nished at least a logical basis for the necessary con- 
clusion that amphimixis was the only possible cause 
of congenital variations. But there is not so much as 
any logical sequence in the now substituted assumption, 
that (A) all congenital variations are ultimately due 
to the wzzversal instability of germ-plasm, and (B) that 
nevertheless they are all more proximately due to such 
a high degree of stability of germ-plasm as necessitates 
amphimixis as the only means whereby variations can 
be made “perceptible.” These statements are as 
independent of one another as any two statements 
can well be; and, therefore, if the second of them is to 


160 An Examination of Wersmanutsm. 


be substantiated, it can only be so by some totally 
distinct line of reasoning. The first statement does not 
even tend to suggest the second ; in fact it tends to 
suggest the precise contrary. For, obviously, there is 
nothing in the logic of the matter to show why, if 
all congenital variations depend for their origin on 
the instability of germ-plasm, such instability must 
nevertheless be always so slight that the variations 
due to it must afterwards depend on amphimixis for 
their development to the point where they become 
“perceptible.” As above indicated, it is surely little 
short of absurd thus to assume that a_ universally 
unstable germ-plasm universally presents only that 
particular degree of instability which will serve to 
accommodate Professor Weismann’s newer theory of 
heredity, and at the same time to save thus much 
of his previous theory of evolution. 

But now, in the second place, not only is this 
assumption wholly gratuitous, but there are many 
considerations which render it in the highest degree 
improbable, while there are not wanting facts which 
appear to demonstrate that it is false. For, unquestion- 
ably, most of the considerations which have already 
been advanced in the preceding chapter against the 
assumption of an absolute stability of germ-plasm, are 
here equally available against the assumption of an 
imperceptibly small amount of instability +. Similarly, 
all the facts there given with regard to the a-sexual 
origin of species—and even genera—of partheno- 


' See especially pp. 86-89. All that is there said about the unicellular 
organisms is not, in the present connexion, affected by Weismann’s 
shange of view with regard to them. We have only to substitute 
“primordial” or ‘‘ protoplasmic” for “ unicellular,” and nearly all the 
points of the criticism remain. 


Wersmannism up to date (1893). 161 


genetic organisms, bud-variation', &c., amply de- 
monstrate that congenital variations due to the 
instability of germ-plasm alone, or apart from amphi- 
mixis, are sometimes enormous. Hence, we cannot 
accept the gratuitous suggestion that in all other 
cases they are too insignificant to count for anything 
till they have been augmented by amphimixis, even 
although we may be prepared to agree that amphi- 
mixis is probably one important factor in the pro- 
duction of congenital variations. What degree of 
importance it presents in this connexion, however, 
we have not at present any means of determining ; 
all we can conclude with certainty is, that in some 
cases it is demonstrably very much less than Weis- 
mann supposes, while it is extremely improbable that 
it is ever in any case the sole and necessary antecedent 
to the operation of natural selection. 

This extreme improbability is shown, not only by 
what I have already said in the previous chapter, and 
need not here repeat ; but likewise by the “ several 
considerations” which Darwin has adduced with 
regard to this very point, and which, as he says, 
“alone render it probable that variability of every 
kind is directly or indirectly caused by changed 
conditions of life,” with the consequence that “ those 
authors who attribute all variability to the mere act 
of sexual union are in error.” I have already quoted 
these words further back in the present chapter, in 
order to show that by now attributing the orzgixz 

1 Professor Weismann has now considered more fully than heretofore 
the phenomena of bud-variation (7he Germ-plasm, pp. 439-442); but 
as he continues (though with diffidence) to take substantially the same 


view of them as that which I have already quoted on pp. 95-96, it is 
needless for me to re-discuss the matter here. 


M 


162 An Examination of Wetsmannism. 


of all congenital variations to the direct action of 
external conditions, Weismann has brought himself 
into line with Darwin so far as this fundamental 
point of doctrine is concerned. But I here re-quote 
the words in order to show that by further attributing 
the development of congenital variations “ to the mere 
act of sexual union,” Weismann is again falling out 
of line with Darwin. So to speak, he first performs | 
a right-about-face movement as regards his original 
position towards the “ stability of germ-plasm,” and 
immediately afterwards makes a half-turn back again. 
Now, it is this half-turn to which I object as un- 
warranted in logic and opposed to fact. 

Ina previous chapter (pp. 66-7) I presented to him 
the dilemma, that germ-plasm must be either ab- 
solutely stable or else but highly stable, and that in 
the former case his theory of amphimixis as the sole 
cause of congenital variations would be valid, while 
in the latter case the theory would collapse. But it 
did not then occur to me that Weismann might seek 
a narrow seat between the horns of this dilemma, by 
representing that germ-plasm is universally unstable 
up to a certain very low degree of instability—viz., 
exactly that degree which is required for starting 
a congenital variation by means of external causes, 
without its being possible for the variation to become 
perceptible unless afterwards increased by means of 
amphimixis. And now that this extremely sophis- 
tical position has been adopted, I cannot see any 
imaginable reason for adopting it other than a last 
endeavour to save as much as possible of his former 
theory of evolution. There can be nothing in the 
nature of things thus to limit, within the narrowest 


Wersmeannism up to date (1893). 163 


possible range, the instability of a universally unstable 
germ-plasm—distributed, as this most complex of 
known substances is, throughout all species of plants 
and animals, and exposed to inconceivably varied 
conditions of life in all quarters of the globe. And 
these considerations are surely of themselves enough 
to dispose of the assumption as absurd, without again 
rehearsing the facts of congenital variation which 
definitely prove it to be false. 


Conclusion. 


For reasons stated at the commencement of this 
chapter, I have restricted its subject-matter almost 
exclusively to a consideration of the more fundamental 
changes which Professor Weismann has wrought in 
his general system of theories by the publication of 
his most recent works. In other words, I have pur- 
posely avoided considering those immensely elaborate 
additions to his theory of heredity which constitute 
by far the largest portion of his essays on Amphimixis 
and Zhe Germ-flasm, and which have for their object 
an ideal construction of “the architecture of germ- 
plasm.” 

The fundamental changes to which allusion has 
just been made are as follows. 

Professor Weismann has to a large extent abandoned 
his theory of polar bodies, and in my opinion would 

M 2 


164 An Examination of Wetsmannism. 


have done well had he taken a further step and 
surrendered the theory zz ¢ofo. 

Similarly, he has withdrawn his previous distinctions 
between the unicellular and multicellular organisms. 
The Protozoa and Protophyta are now included by 
him in the same category as the Metazoa and Meta- 
phyta, as regards all matters of individual variation, 
reproduction, subjection to the law of natural selection, 
and so forth. The only difference which he continues 
to allege is the somewhat metaphysical one touching 
mortality and immortality. But I have given what 
appears to me sufficiently good reasons for ignoring 
this: distinctions "and therefore, as’ it’ seems. to: me, 
every one of Weismann’s previous doctrines respecting 
unicellular organisms have vanished—very much to 
the benefit of his system as a whole. 

By far the greatest change, however, which he has 
made in this general system is that which he has 
effected by surrendering the postulate of the absolute 
stability of germ-plasm. The rift in his lute which 
has been noticed with regard to this matter has 
now been widened to an extent which does prevent 
any further harping on the theme of evolution. It 
is true that Weismann endeavours to retain as far as 
possible the general character of his former postulate 
of the universal stability of germ-plasm, with the 
consequent “significance of sexual reproduction” as 
the sole cause of congenital variation. For although 
he now reverses both these doctrines by saying that 
germ-plasm is universally unstable, and that sexual 
reproduction is in no case the sole cause of congenital 
variation, he seeks at the same time to minimize the 
logical consequences of such reversal by making an 


Wersmannism up to date (1893). 165 


ingenious assumption, the possibility of which I had 
not foreseen when writing the previous chapters. 
The assumption is, that although germ-plasm is 
universally unstable, the degree of its instability is 
everywhere restricted within the narrowest possible 
limits ; so that sexual propagation is still necessary 
for the purpose of developing congenital variations to 
the point where they can fall within the range of 
natural selection, notwithstanding that they must all 
have been originated by external causes acting 
directly on a germ-plasm universally unstable within 
the narrow limits assumed. But clearly this as- 
sumption is arbitrary to the last degree, and, no less 
clearly, it is made by Weismann for the sole purpose 
of saving as much as he can of his previous theory of 
variation. His more recent speculations touching 
the mechanism of heredity are incompatible with his 
former view of amphimixis as the so/e cause of con- 
genital variations, and therefore he makes this arbitrary 
assumption for the purpose of representing that am- 
phimixis may nevertheless still be regarded as 
a necessary con-cause. I need not here repeat what 
has so recently been said touching the sophistry of this 
assumption in theory, or the demonstrable falsity of it 
in fact. It is enough to remark, in conclusion, that 
the game is not worth the candle. It was originally 
well worth Weismann’s while to sustain his funda- 
mental postulate of the absolute stability of germ- 
plasm, because he was able to rear upon it his whole 
theory of evolution. But the only part of this theory 
which he has now left standing, or which he can now 
save by his newer postulate of a germ-plasm both stable 
and unstable at the same time, is his doctrine of 


166 An Examination of Wersmannism., 


variation. So to speak, it is his desire to reserve as 
much as is speculatively possible from the general © 
ruin of his theory of descent, that causes him to go so 
far to attempt so little. For I cannot suppose that he 
himself will expect any of his readers to entertain 
so arbitrary, fanciful, and demonstrably false an 
assumption as the one in question. Surely it would 
have been better to have surrendered 72% Zofo this 
“ Weismannian theory of variation,’ rather than to 
have attempted its rescue by means so _ plainly 
nugatory. It might still have been held that amphi- 
mixis plays a large and important part as one of the 
causes of variation, and therefore also as one of the 
factors of organic evolution. After having reversed 
his postulate of amphimixis being the sole cause of 
variability, and therefore having agreed with Darwin 
that “those writers are in error who attribute all 
variability to the mere act of sexual union,” he might 
well have questioned Darwin’s further statement as to 
its being “probable that variability of every kind is 
directly or indirectly caused by changed conditions 
of life.” But by now assuming that variations due to 
any causes other than amphimixis must be ‘“ imper- 
ceptible” until they have been augmented by amphi- 
mixis, Weismann is shutting out, with a futile hypo- 
thesis, the important question as to whether, or how 
far, amphimixis really is a cause of variation. Observe, 
the case is not as it might have been were there no 
reasons assignable for the occurrence of sexual pro- 
pagation, other than that of assisting in the production 
of congenital variations. The theory of ‘ rejuve- 
nescence,’ for example, is przma facie a more probable 
one than that which ascribes to sexual propagation 


Wersmannism up to date (1893). 167 


the function of causing variability!; while Galton’s 
hypothesis, which supposes the object of this form of 
propagation to be that of conserving the “germs”’ 
(=“determinants”) of the phyla, has a good deal 
to say for itself*. Of course such alternative hypo- 


'«« Rejuvenescence”” means the renewal of vital energies which is 
supposed to result from a fusion of the contents of two cells. For an 
excellent discussion of this and the other theories on the object of sexual 
propagation, see a brief article by Professor Marcus Hartog, in the 
Contemporary Review for July, 1892. Since then Weismann has published 
The Germ-plasm, and here his main argument against this theory is that 
tens, or even hundreds of generations of unicellular organisms have been 
observed to succeed one another before any act of conjugation takes 
place. But I cannot see that it signifies how many generations may in 
different species be proved capable of resulting from a single act of con- 
jugation. Weismann himself now accepts the analogy between cell- 
proliferation as resulting from conjugation in unicellular organisms, and 
from fertilization in multicellular. But even three hundred generations 
of the former can scarcely be regarded as equal to all the “‘ ontogenetic 
stages” of the latter. 

* This view of the function of sexual propagation is now universally 
ascribed to Strasburger, and it is quite true that he has independently 
adduced it. But as this was not done until about ten years after it had been 
published by Galton, I have designedly associated the idea with Galton’s 
name. The following are the words in which it was announced 
by him :— 

‘The necessity of a system of double parentage in complex organisa- 
tions is the immediate consequence of a theory of organic units and 
germs, as we shall see if we fix our attention upon any one definite series 
of unisexual descents, and follow out its history. Suppose we select, 
cut off, and plant the second bud, then after it has grown to maturity we 
similarly take the second of z¢s buds, and so on consecutively. At each 
successive stage there is always a chance of some one or more of the 
various species of germs in the stirp dying out, or being omitted; and of 
course when they are gone they are lost for ever, and are irreplaceable 
by others. From time to time this chance must fall unfavourably, and 
will cause a deficiency in some of the structural elements, and a conse- 
quent deterioration of the race. If the loss be vital, this particular line 
of descent will of course be extinguished at once; but on the more 
favourable supposition, the race will linger on, submitting to successive 
decrements in its constituent elements, until the accumulation of small 
losses becomes fatal.”’—/oc. czt., p. 333. 

Galton also points out a further advantage that is secured by 


168 An Examination of Wetsmannism. 


theses touching “the significance of sexual repro- 
duction” are not necessarily exclusive of one another : 
the process may subserve two or more adaptive 
purposes’. But he would be a bold man who, in the 
present state of our knowledge. could accept unre- 
servedly the particular view of this process which 
Darwin so emphatically rejected; and I think he 
must be a biased man who could entertain for 
an instant the modification of this view which Weis- 
mann has now substituted. 

Thus, the Weismannian theory of evolution has 
entirely fallen to pieces with the removal of its 
fundamental postulate—the absolute stability of 
germ-plasm. It only remains to mention once more 
the effects of this removal upon the other side of his 
system—viz., the companion postulate of the uninter- 
rupted continuity of germ-plasm, with its superstructure 
in his theory of heredity. 

Briefly, these effects are as follows :— 

1. Germ-plasm ceases to be continuous in the 
sense of having borne a perpetual record of con- 
‘¢amphimixis,” and one which shows the non-necessity of what remains 
of Weismann’s theory of polar bodies, thus— 

** There is yet another advantage in double parentage, namely, that as 
the stirp whence the child sprang can only be half the size of the 
combined stirps of his two parents, it follows that one half of his possible 
heritage must have been suppressed. ‘This implies a sharp struggle for 
place among the competing germs, and the success, as we may infer, 
of the fitter half of their numerous varieties.” —/oc. czt., p. 334. 

1 In fact, it seems to me that this is the sole supposition whereby it 
can be held that sexual propagation has been developed both “ by” and 
‘‘ for” natural selection, in order to supply variations as material for the 
action of this principle. Natural selection cannot thus supply the 
conditions to its own activity, if, as Weismann supposes, there is but 
one purpose for it to subserve (see above, pp. 13-15). But, if it 


is acting for more than one purpose, the ‘‘ by” and the “for” argument 
may hold. 


Weismannism up to date (1893). 169 


genital variations from the first origin of sexual 
propagation. 

2. On the contrary, as all such variations have 
been originated by the direct action of external 
conditions, the continuity of germ-plasm in this sense 
has been interrupted at the commencement of every 
inherited change during the phylogeny of all plants 
and animals, unicellular as well as multicellular. 

3. But germ-plasm remains continuous in the 
restricted, though still highly important sense, of 
being the sole repository of hereditary characters of 
each successive generation, so that acquired characters 
can never have been transmitted to progeny “ repre- 
sentatively,” even although they have frequently 
caused those “specialized’”’ changes in the structure 
of germ-plasm which, as we have seen, must certainly 
have been of considerable importance in the history 
of organic evolution. 

4. By surrendering his doctrine of the absolute} 
stability of germ-plasm on the one hand, and of its 
perpetual’ continuity on the other, Weismann has 
greatly improved his theory of heredity. For, what- 
ever may be thought of his recent additions to this 
theory in the way of elaborate speculation touching 


1 T find that a passage explaining the sense in which I use these terms 
has been accidentally omitted from Chapter III, where they are first 
introduced ; and, as the sheets of that chapter have been already printed 
off, I here supply the omission. The terms in italics are not Weismann’s, 
and I have employed them merely for the purpose of giving precision to 
his views. By “ absolute stability of germ-plasm” I mean to indicate 
that degree of stability which he has hitherto postulated as the necessary 
basis for his doctrine of heritable variations being solely due to admix- 
tures of germ-plasm in sexual unions. By “ Zerpetual continuity of 
germ-plasm” I intend to denote that amount of continuity which he still 
postulates as the necessary basis for his correlative doctrine touching the 
non-inheritance of acquired characters. 


170 An Examinatin of Wersmannism. 


the ultimate mechanism of heredity, it is a great 
gain to have freed his fundamental postulate of the 
continuity of germ-plasm from the two further 
postulates which have just been mentioned, and the 
sole purpose of which was to provide a basis for his 
untenable theory of evolution. 

5. In my opinion it only remains for him to 
withdraw the last remnant of his theory of evolution 
by cancelling his modified and even less tenable 
views on amphimixis, in order to give us a theory of 
heredity which is at once logically intact and _ bio- 
logically probable. 

6. The theory of germ-plasm would then resemble 
that of stirp in all points of fundamental importance, 
save that while the latter leaves the question open as 
to whether acquired characters are ever inherited in 
any degree, the former would dogmatically close it, 
chiefly on the grounds which I have considered in 
Appendix II. It seems to me that in the present 
state of our knowledge it is more prudent to follow 
Galton in suspending our judgement with regard to 
this question, until time shall have been allowed for 
answering it by the inductive methods of observation 
and experiment. 

7. Hence, in conclusion, we have for the present 
only to repeat what Weismann himself has said in 
one of the wisest of his utterances,—“ The question 
as to the inheritance of acquired characters remains, 
whether the theory of germ-plasm be accepted or 
rejected.” 

It is now close upon twenty years that I accepted 
the substance of this theory under the name of stirp ; 
and since that time the question as to the inheritance 


Wersmannism up to date (1893). 171 


of acquired characters remains exactly where it was. 
No new facts, and no new considerations of much 
importance, have been forthcoming to assist us in 
answering it. Therefore, as already stated in the 
Preface, I intend to deal with this question hereafter 
as a question per se. or one which is not specially 
associated with the labours of Professor Weismann. 


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ON GERM-PLASM. 


As already stated in the text (p. 71), Weismann’s general 
reasoning in support of his own theory of germ-plasm, as 
against Darwin’s theory of gemmules in any form, admits 
of being reduced to arguments in favour of three proposi- 
tions—viz., first, that there is no evidence of the transmission 
of somatogenetic characters ; secondly, that the theory of pan- 
genesis, which seeks to explain their supposed transmission, 
is “inconceivable”; and, thirdly, that its logical antithesis— 
the theory of germ-plasm—is so much less beset with 
difficulties, that by comparison it is simple, self-coherent, 
and offers a real, as distinguished from a ‘‘ formal,” ex- 
planation of the facts of heredity. 

The first of these propositions will be discussed at con- 
siderable length in my next volume. The second and third 
propositions, however, may be dealt with here. 

The following paragraph, which I shall quote sentence 
by sentence, sets forth the grounds on which Weismann bases 
the second proposition, namely, that any theory belonging 
to the order of pangenesis—i. e., which supposes the carriers 
of heredity ever to travel centripetally—is, from its very 
nature, inconceivable. 


At first sight this hypothesis seems to be quite reasonable. 
It is not only conceivable that particles might proceed from the 
somatic to the reproductive cells, but the very nutrition of the 


174. An Examination of Weismannism. 


latter at the expense of the former is a demonstration that such 
a passage actually takes place. But a closer examination reveals 
immense difficulties. In the first place, the molecules of the 
body devoured are never simply added to those of the feeding 
individual without undergoing any change, but, as far as we 
know, they are really assimilated, that is, converted into the 
molecules of the latter. We cannot therefore gain much by 
assuming that a number of molecules can pass from the growing 
somatic cells into the growing reproductive cells, and can be 
deposited unchanged in the latter, so that, at their next division, 
the molecules are separated to become the somatic cells of the 
following generation '. 


The obvious answer to this is, that no one has ever 
supposed “gemmules” to be merely “molecules,” in the 
chemical sense of this word; nor has any one ever imagined 
that they are “devoured” by the germ-cells into which they 
pass. Of course, if this were the case—i.e., if gemmules serve 
merely as food to the germ-cells—they would become disin- 
tegrated down even to their chemically molecular structure, 
and there would be an end of them as organized “ carriers 
of heredity.” 

In the second place, it is asked :-— 


How can such a process fi.e. the passage of gemmules into 
growing germ-cells|] be conceivable, when the colony becomes 
more complex, when the number of somatic cells becomes so 
large that they surround the reproductive cells with many 
‘layers, and when at the same time, by an increasing division 
of labour, a great number of different tissues and cells are 
produced, all of which must originate de zovo from a single 
reproductive cell? 


Here, again, the obvious answer is, that no one has ever 
propounded such a statement. Far from supposing that 
‘all the different cells and tissues of a complex organism 


1 Essays, pp. 76-77, from which the following quotations are likewise 
taken serzatim. 


Appendix TL, 175 


must originate de novo from a szzgle reproductive cell,” the 
theory of pangenesis supposes the very contrary—viz., that 
somatic changes in the past history of the phyla have zof 
thus originated in amy reproductive cell. The idea of 
somatic changes originating in reproductive cells belongs 
to the theory of germ-plasm; but even this theory does 
not suppose all the great number of different cells and 
tissues which compose a complex organism to have ever 
originated de novo from a szmgle reproductive cell. 

The difficulty touching germ-cells becoming isolated, or 
buried, by the phylogenetic increase of somatic cells, is 
enforced in the immediately succeeding sentences, thus :— 


Each of these various elements [somatic cells] must, ex 
hypothesi, give up certain molecules to the reproductive cells ; 
hence those which are in immediate contact with the latter 
would obviously possess an advantage over those which are 
more remote. If, then, any somatic cell must send the same 
number of molecules to each reproductive cell ', we are compelled 
to suspend all known physical and physiological conceptions, 
and must make the entirely gratuitous assumption of an affinity 
on the part of the molecules for the reproductive cells. Even if 
we admit the existence of this affinity, its origin and means of 
control remain perfectly unintelligible if we suppose that it has 
arisen from differentiation of the complete colony. An unknown 
controlling force must be added to this mysterious arrangement, 
in order to marshal the molecules which enter the reproductive 
cell in such a manner that their arrangement corresponds with 
the order in which they must emerge as cells at a later period. 


Now I do not see much force in the suggestion that 
those somatic cells which happen to be in immediate con- 
tact with germ-cells, “‘must obviously possess an advantage 


1 «¢ Or, more precisely, they must give up as many molecules as would 
correspond to the number of the kind of cell in question found in the 
mature organism.” Of course by ‘‘molecules”” Weismann means what 
Darwin does by ‘‘ gemmules.”’ 


176 An Examination of Wetsmannism. 


over those which are more remote.” On the contrary, I 
do not see that mere proximity of one species of cell to 
another species within the same organism need have any- 
thing to do with the matter—still less that “we must 
suspend all physical and physiological conceptions,” if we 
demur to the statement that it “obviously must.’ As for 
‘physical conceptions,’ how many thousands of cases might 
not be pointed to among chemical and mechanical pro- 
cesses where contact or proximity are conditions of com- 
paratively little importance? And as for “physiological 
conceptions,’ do we find that any part of the organism is 
affected by its distance, say, from the liver and kidneys, 
for getting rid of its effete products? Is it not rather the 
case that every gland in the body is wholly unaffected by 
its distance from any part of the body, in regard to its 
function of draining off the particular substances with which 
it is concerned? Why then should the reproductive gland 
constitute a conspicuous exception? Or how do we sus- 
pend all physiological conceptions, if we suppose that this 
gland resembles every other gland in being specialized to 
secrete a particular kind of “ molecule,’ which, because thus 
specially selected, may be said to have for that gland a 
special “affinity”? If there are such things as gemmules, 
I do not see any violation of physiological analogies—still 
less an ‘entirely gratuitous assumption’”—in supposing 
that they can be filtered out from all parts of the body by 
the sexual glands, and there aggregated as a special product 
to be discharged in the form of sexual elements’. 


1 If there are such things as gemmules, it appears to me to follow 
that the only physiological distinction between the reproductive glands 
and glands in general is, that the former discharge their products in the 
form of living cells. Even here, however, there appears to be one 
analogous case in those salivary glands which discharge the so-called 
salivary corpuscles—i.e., nucleated cells, undergoing amoeboid changes 
of form, and exhibiting the movements of living protoplasm in their 
interior. 


Appendix I, 177 


But, it is further represented, “even if we admit the 
existence of this affinity, an unknown controlling force 
must be added to this mysterious arrangement, in order 
to marshal the molecules which enter the [growing] repro- 
ductive cell in such a manner that their arrangement 
corresponds with the order in which they emerge as cells 
at a later period.” Surely, however, for Weismann of all 
naturalists it ought not to be difficult to find this “unknown 
controlling force.” For of all naturalists he is perhaps the 
most ready to invoke the agency of natural selection as 
sufficient to explain every case—actual or imaginable—of 
adaptation. Now, here is a case where natural selection, 
one would think, is positively bound to act—supposing 
that there be such things as gemmules. For, if ‘the 
carriers of heredity” are gemmules, it is evident that their 
mutual “affinities” must be adaptively “marshalled” at 
each step of phylogenetic evolution, before any further 
advance of such evolution can be possible. And I do 
not see anything more “inconceivable” in supposing the 
establishment of such mutual affinities step by step through 
natural selection, than in supposing any other course of 
adaptive development by similar means. For, as Darwin 
has well shown, while anticipating this particular objection 
to his theory,—‘‘ The assumed elective affinity of each 
gemmule for that particular cell which precedes it in due 
order of development is supported by many analogies.” 
The analogies which he then gives are so numerous that 
I must here refer to his own discussion of the subject'— 
a discussion which is entirely ignored by Weismann. 

Lastly, the principal ground, as far as I can see, 
which Weismann has for regarding Darwin’s theory in 
any shape “ inconceivable,’ is his own supposition that 
there is as complete an anatomical separation between the 


! Variation, &c., 2nd ed., vol. ii. pp. 374-6. 
N 


/ 


178 An Examination of Wetsmannism. 


soma and its germ-cells as there is, for example, between 
the mammalian soma and these same cells when afterwards 
detached from the ovary and developing as foetuses 7 
utero. In other words, the only connexion is supposed 
to be that of deriving nourishment by way of imbibition. 
But, as regards the germ-cell while still forming in the 
ovary or testicle, there is for this supposition no basis in 
fact. There is nothing in the histology of spermatogenesis 
that lends countenance to the supposition, while in the case 
of the ovum such histological evidence as we possess makes 
altogether against it. As Professor Vines has remarked :— 


It cannot be seriously maintained that the whole body of the 
embryo is developed solely from the germ-plasm of the ovum. 
On the contrary, since the embryo is developed from the whole 
of the nucleus and more or less of the cytoplasm of the ovum, 
it must be admitted that the non-germ-plasm of the ovum 
provides a large part of the material in embryogeny. It is an 
obvious inference that, under these circumstances, hereditary 
characters may be transmitted from the parent to the offspring, 
not only by the germ-plasm, but also by the somato-plasm, of the 
ovum |. 


Again, and apart from this consideration, it is now 
known that a very intimate network of protoplasmic fibres 
connects the cell-contents of cellular tissues, both in plants 
and animals. So that here we have another very possible 
means of communication between the germ-cells and the 
somatic-cells which together constitute a multicellular 
organism, 

Therefore, in so far as histology can be trusted to 
constitute a basis for generalizations of this kind at all, it 
does not sustain the supposition that there can be no 
medium of communication between the general cellular 


1 Nature, vol. xl. p. 624. Weismann’s answer to this and other parts 
of Professor Vines’ criticism where the term ‘‘somato-plasm” occurs, will 
be considered later on. ; 


Appendix Tf, 179 


tissues of an organism and its specially reproductive 
elements. On the contrary, the microscope is able to 
demonstrate possible roads of connexion—and this even 
upon Weismann’s own view as to a specialized germinal 
substance which is restricted to the nucleus of an ovum. 
In short, the supposition as to an absolute anatomical 
separation between germ-plasm and somato-plasm is a de- 
duction from Weismann’s theory itself: it is not supported 
—it is discredited—by histological observation. Hence, 
it cannot be accepted as valid evidence in favour of the 
theory from which alone it is derived, or as a valid 
objection to the rival theory of pangenesis. 

Once more, even if it were true that histology proves 
an absolute anatomical isolation on the part of germ-cells, 
it would still have remained unquestionable that there is no 
absolute physzological isolation. For, at least, the germ- 
plasm derives its nourishment from the soma in which it 
resides ; and who shall say that the process of mere imbibi- 
tion is not amply sufficient to admit of the passage of 
“oemmules”? Call them what we choose, the “carriers 
of heredity’ must be so unimaginably small, that in relation 
to histological cells they must be as gnats to camels. Yet 
we know that even camels in the form of “migrating cells” 
of various kinds are able to pass through living membranes ; 
and we also know that the microbes of syphilis can 
penetrate both ova and spermatozoa. Why then should it 
be deemed inconceivable that, where all such things can 
pass, gemmules can do so likewise? 

Lastly, I have recently spoken of the detached condition 
of a ripe ovum zz ulero. Now it seems to me more “in- 
conceivable” that such an ovum should be capable of 
announcing, as it were, to the walls of the uterus whether or 
not it is in a fertilized condition, than it is that, before quit- 
ting the ovary, it should have had some kind of physiological 
converse with its environing soma. Yet it is certain that, 

N 2 


180 An Examination of Wetsmannism. 


without any visible medium of communication, the impreg- 
nated ovum is able to inform the uterus that it is impreg- 
nated; and thereupon the uterus behaves towards that 
ovum in an altogether astonishing manner, such as it never 
displays towards an unimpregnated ovum. Of course various 
hypotheses may now be formed to account for this fact, 
seeing that no one can question it as a fact. But sup- 
posing that the fact could be questioned, with how much 
greater effect might it be argued that any communication 
between the ovum and its soma is even more antecedently 
incredible when the ovum is entirely free than when it is 
still contained within its ovary. 

Now these, as far as I can find, are the only grounds 
for Weismann’s repeated assertion that the theory of pan- 
genesis in any form is “inconceivable.” I have therefore 
endeavoured to show that this is too strong a statement. 
All the facts and considerations whereby he seeks to support 
it were present to the mind of Darwin; and, quite apart from 
any question of relative authority, I cannot avoid agreeing 
with Darwin that, whether or not the theory is true, at all 
events the “difficulties” attaching to it on these merely 
a prior? grounds are not insuperable, or such as to render 
his ‘‘pet child” an unconceived monstrosity in logic, or 
a proved absurdity in science. 

Be it understood, however, that I am not here defending 
the theory of pangenesis, I am investigating the theory 
of germ-plasm; and it is because Weismann seeks to 
sustain the latter by excluding the former as preposterous, 
that I have been obliged thus to consider the validity of 
his criticism. For the point to which I am leading is, 
that Weismann gains nothing in the way of support to 
his own theory by this disparagement of Darwin’s, unless 
he can show that the former supplies some more “ conceivable” 
explanation touching the mechanism of heredity. Now 1 am 
unable to see that he has shown this. What I do see 


Appendix Tf, 181 


is that his @ przord argument from “inconceivability ” 
cuts both ways, and that it makes at least as much against 
germ-plasm as it does against gemmules. Therefore, 
having now considered what Weismann has said against 
the conceivability of gemmules on grounds of general 
reasoning, I shall proceed to show that quite as much— 
or even more—may be said in the way of a fu quoque. 
In other words, we have now finished with the second of 
the three propositions which we are examining (see p. 71), 
and proceed to our consideration of the third. ; 

First of all, I do not see any greater difficulty in 
supposing that the “carriers of heredity” proceed centri- 
petally from somatic-cells to germ-cells, than in supposing that 
they proceed centrifugally from the germ-cells to the somatic- 
cells which they are engaged in constructing. Nor do I 
see any more difficulty in imagining these “carriers of 
heredity” to be capable of constructing a new organism 
if they have first proceeded centripetally, and are thus 
severally representative of all parts of the parent organism 
after ws construction has been completed, than I do if they 
have proceeded centrifugally, and are thus similarly repre- 
sentative of all parts of that organism Jdefore tts construction 
has been commenced’. 


' Weismann speaks disparagingly of Darwin’s theory as a ‘‘ theory 
of preformation”’ (p. 316). ‘*We must assume,” he adds by way of 
explanation, “that each single part of the body at each developmental 
stage is, from the first, represented in the germ-cell as distinct particles 
of matter, which will reproduce each part of the body at its appropriate 
stage as their turn for development arrives.” But must we not likewise 
“assume” exactly the same thing in the case of Weismann’s own 
theory? To me, at any rate, it appears that the description is quite as 
appropriate to germ-plasm as it is to gemmules. Nor can I see any 
distinction, even where he seeks to draw it more expressly, as for 
instance—‘‘ Every detail in the whole organism must be represented in 
the germ-plasm by its own special and peculiar arrangement of the 
groups of molecules, .. . not indeed as the preformed germs of structure (the 
gemmules of pangenesis), but as variations in its molecular constitution.” 
[ Essays, p. 194.) Again, on page 325 he gives a foot-note explaining 


182 An Examination of Wersmanuism. 


Similarly, it seems to me, whatever cogency there may be 
in Weismann’s objection to Darwin’s theory on the score 
that it must assume “an unknown controlling force in order 
to marshal the molecules,” is equally great as regards his 
own. True, Weismann has a lot to say about the control 
which nucleo-plasm can exercise on cell-formation, and 
germ-plasm on marshalling successive stages of ontogeny ; 
but all that this amounts to is a re-statement of the facts. 
Such a controlling force must be equally assumed by both 
theories ; but in each alike there is an absence of any ghost 
of an explanation. 

Again, whatever difficulty there may be in conceiving 
the transition of somatic substance, mutatis mutand?s there 
must be an equal difficulty in conceiving the transition of 
germinal substance into somatic substance. Indeed, as far 
as I can see, the difficulty is even greater in the latter case 
than it is in the former. For the very essence of Weismann’s 
view is that germ-plasm differs from all or any other 
“plasm” in origin or kind: germ-plasm, and germ-plasm 
alone, has been immortal, perpetually continuous, capable 
of indefinite self-multiplication, and so of differentiating 
itself into an endless number and variety of somatic tissues. 
But, according to Darwin’s view, there is not, and never 
has been, any such fundamental difference between the 
essential nature of somatic elements, and the essential 
nature of sexual elements. On the contrary, it is supposed 
that both formative and formed material are one in kind 


the distinction by alluding to the controversy between the preformation- 
ists and epigenesists. But the theory of pangenesis does not suppose the 
future organism to exist in the egg-cell as a miniature: it supposes 
merely that every part of the future organism is represented in the egg- 
ceil by corresponding material particles. And this, as far as I can 
understand, is exactly what the theory of germ-plasm supposes; only 
it calls the particles ‘‘molecules,” and seemingly attaches more im- 
portance to the matter of variations in their arrangement or “constitution,” 
whatever these vague expressions may be intended to signify. 


Appendx TI, 183 


—that all the cellular tissues of a multicellular organism, 
like the single cell of a unicellular organism, are per se 
endowed with the vital property of self-multiplication; and 
that whether this property finds its expression in normal 
growth, in abnormal increments of growth (such as tumours), 
in processes of repair, in the various forms of a-sexual 
reproduction, or in the more specialized form of sexual 
fertilization, there is everywhere an exhibition of one and 
the same capacity. Now, without going further than this 
contrast between the fundamental principles of the two 
theories, does it not become evident that the difficulty of 
conceiving a transition of A into A’ is at any rate no 
greater than that of conceiving a transition of A into B, 
where A is in both cases the formative substance, A’ this 
same substance in another stage of evolution (i.e., elaborated 
for the performance of some special function, but never 
so as to lose its original function A), while B is a substance 
which differs from A almost as much as a woven texture 
differs from the hands that weave it? 

Once more, in all his arguments which are directed to 
prove the continuity of germ-plasm, Weismann nowhere 
seems to perceive the necessity of arguing the correlative 
hypothesis—viz., that of the discontinuity of somato-plasm. 
Yet, as Professor Vines has remarked, it is as incumbent 
on him to disprove any possible continuity on the part of 
somato-plasm, as it is to prove a perpetual continuity on 
the part of germ-plasm. And here I am disposed to go 
further than Professor Vines has gone; for it appears to me 
even more incumbent on Weismann to argue a discontinuity 
on the part of somato-plasm, than it is on him to argue 
a continuity on the part of germ-plasm. 

This must be immediately apparent if we remember that, 
unless the discontinuity of somato-plasm be assumed, the 
theory of the continuity of germ-plasm in telluric time (as 
distinguished from eternity) becomes identical in form with 


184 An Examination of Wersmannism. 


all those theories of heredity to the family of which pan- 
genesis belongs. All these theories go upon the assumption 
that living material has been continuous in telluric time— 
i.e., always derived from pre-existing material of the same 
kind; but they embody the further assumption that ad/ living 
material zs material of the same kind —ji.e., everywhere 
presents the same fundamental properties. Weismann’s 
theory on the other hand, while adopting the first assump- 
tion, rejects the second; and assumes in its stead that living 
material exists in “two kinds,” only one of which has been 
continuous, while the other is discontinuous—being, in fact, 
formed anew at each ontogeny. ‘Therefore, to my mind, it 
seems more needful to argue the point wherein his theory 
differs from these other theories of heredity, than it is to 
argue the point wherein it agrees with them. We look to 
him for a proof of the discontinuity of somato-plasm much 
more than we do for a proof of the continuity of germ-plasm. 
Now the only proof that he has to give of the discontinuity 
of somato-plasm—or, in other words, that the self-multiplica- 
tion of somatic cells cannot take place unless the nucleus of 
each contains a self-multiplying idio-plasm derived from the 
nucleus of a germ-cell—is the non-transmissibility of somato- 
genetic characters. Here, however, there is an obvious 
equivoque. For his only test of characters as somatogenetic 
and blastogenetic consists in observing whether or not they 
are inherited: if they are inherited, he says they are blasto- 
genetic: if they are not inherited, he says they are somato- 
genetic. But this is manifestly circular reasoning, so long 
as the question in debate is as to the truth of his theory. 
What we require in proof of the distinguishing feature of that 
theory —i.e., the discontinuity of the hypothetical somato- 
plasm—is not merely the obvious fact that some characters 
are inherited while others are not, but independent proof 
that inherited and non-inherited characters correspond to 
a continuity of germ-plasm on the one hand, and a dis- 


Appendix TL, 185 


continuity of somato-plasm on the other. He shows us, 
indeed, what was well known before, that characters developed 
during the lifetime of the individual are seldom (if ever) 
inherited, while’ characters developed during the lifetime of 
the species are always inherited. Obviously, however, this 
fact is no proof of the assumed correlation just mentioned, 
because, as Darwin has clearly pointed out, it may very well 
be due to the much shorter time which has been allowed for 
what may be termed the impress of heredity. ‘Therefore, 
supposing (with Darwin and others) that living material is all 
of one kind, and continuous, the fact on which Weismann 
relies admits of being explained without resorting to his more 
complex supposition of living material in two kinds, the one 
perpetually continuous, and the other interrupted at each 
ontogeny. 

For these reasons it appears to me that, so far as the 
argument from “ inconceivability ” is concerned, it makes at 
least as much against the theory of germ-plasm as it does 
against the theory of pangenesis; and, therefore, that no 
argumentative advantage is gained from its use by Weismann. 
The truth probably is that, whatever the mechanism of 
heredity may actually be, it is at once so minute and 
so complex that its action is “inconceivable,” or, more 
correctly, unimaginable. Be it again understood, therefore, 
that I am not arguing in favour of pangenesis. I am merely 
criticising what appears to me an unsound argument in 
favour of germ-plasm. All this general or merely a prior? 
reasoning with regard to inconceivability is, as I have 
attempted to show, as available on the one side as on the other, 
and so fails to yield any observable advantage to either. 


In conclusion it must be noticed, that Weismann now 
appears to have himself perceived the grave difficulties which 
lie against his antithesis between a hypothetical “ germ- 
plasm ” and a hypothetical ‘“‘ somato-plasm,” notwithstanding 


186 An Examination of Wetsmannism. 


that the former becomes converted into the latter at each 
ontogeny. At any rate, he allows that Vines’ criticism upon 
this head is sound. But he is strongly of the opinion that, 
by means of a later emendation of his theory as originally 
published, he has succeeded in obviating these difficulties 
in toto. For my own part, as already several times observed 
in the text, I cannot in the least perceive that such is the 
case; and therefore I will quote 2% ex/enso what he has said 
in answer to Professor Vines. It will be seen that his newer 
emendation of the theory consists in substituting for his 
original “somato-plasm” two substances, which are called 
respectively ‘somatic idio-plasm” and “cytoplasm.” And 
it is by means of this substitution that he thinks he has, in 
some way or another, overcome the contradiction involved in 
the doctrine (and, as it still seems to me, the essential 
doctrine of his whole theory of heredity) that “ germ-plasm ” 
becomes converted into ‘“‘somato-plasm” during the course 
of every ontogeny. The following, at any rate, is his latest 
utterance upon the subject :— 


I believe that the objections which Professor Vines makes to 
my theory of the continuity of germ-plasma rest solely on an 
unintentional confusion of my ideas, as he compares the opinions 
expressed in the second essay with those of the later ones, 
with which they do not tally. I will endeavour to make this 
clear. In this second essay (1883) I contrasted the body (soma) 
with the germ-cells, and explained heredity by the hypothesis 
of a “ Vererbungs-substanz” in the germ-cells (in fact the germ- 
plasma), which is transmitted without breach of continuity from 
one generation to the next. I was not then aware that this lay 
only in the nucleus of the ovum, and could therefore contrast 
the entire substance of the ovum with the substance of the 
body-cells, and term the latter “‘somato-plasm.” In Essay IV 
(1885) 1 had arrived, like Strasburger and O. Hertwig, at the 
conviction that the nuclear substance, the chromatin of the 
nuclear loops, was the carrier of heredity, and that the body of 
the cell was nutritive but not formative. Like the investigators 


Appendix TI. 187 


just named, I transferred the conception of idio-plasm, which 
Nageli had enunciated in essentially different terms, to the 
“ Vererbungs-substanz” of the ovum-nucleus, and laid down 
that the nuclear chromatin was the idio-plasm not only of the 
ovum but of every cell, that it was the dominant cell-element 
which impressed its specific character upon the originally 
indifferent cell-mass. From then onwards, I no longer desig- 
nated the cells of the body simply as “somato-plasm,” but 
distinguished, on the one hand, the idio-plasm or “ Anlagen- 
plasma” of the nucleus from the cell-body or “Cytoplasma,” 
and, on the other, the idio-plasm of the ovum-nucleus from that 
of the somatic cell-nucleus ; I also for the future applied ‘‘ germ- 
plasm” to the nuclear idio-plasm of ovum and spermatozoon, 
and ‘ somatic idio-plasm” to that of the body cells (e.g, p. 184). 
The embryogenesis rests, according to my idea, on alterations 
in the nuclear idio-plasm of the ovum, or “‘germ-plasm”; on 
p. 186, et seq., is pictured the way in which the nuclear idio- 
plasm is halved in the first cell-division, undergoing regular 
alterations of its substance in such a way that neither half 
contains all the hereditary tendencies, but the one daughter- 
nucleus has those of the ectoblast, the other those of the ento- 
blast; the whole remaining embryogenesis rests on a con- 
tinuation of this process of regular alterations of the idio-plasm. 
Each fresh cell-division sorts out tendencies which were mixed 
in the nucleus of the mother-cell, until the complete mass of 
embryonic cells is formed, each with a nuclear idio-plasm which 
stamps its specific histological character on the cell. 

I really do not understand how Professor Vines can find such 
remarkable difficulties in this idea. The appearance of the 
sexual cells generally occurs late in the embryogeny ; in order, 
then, to preserve the continuity of germ-plasm from one 
generation to the next, I propound the hypothesis that in 
segmentation it is not a// the germ-plasm (i.e., idio-plasm of the 
first ontogenetic grade) which is transformed into the second 
grade, but that a minute portion remains unaltered in one of 
the daughter-cells, mingled with its nuclear idio-plasm, but in 
an inactive state; and that it traverses in this manner a longer 
or shorter series of cells, till, reaching those cells on which it 
stamps the character of germinal cells, it at last assumes the 


188 An Examination of Wersmannism. 


active state. This hypothesis is not purely gratuitous, but is 
supported by observations, notably by the remarkable wander- 
ings of the germinal cells of Hydroids from their original 
positions. 

But let us neglect the probability of my hypothesis, and 
consider merely its logical accuracy. Professor Vines says :— 
“ The fate of the germ-plasm of the fertilized ovum is, according 
to Professor Weismann, to be converted in part into the somato- 
plasm (!) of the embryo, and in part to be stored up in the 
germ-cells of the embryo. This being so, how are we to conceive 
that the germ-plasm of the ovum can impress upon the somato- 
plasm (!) of the developing embryo the hereditary character of 
which it (the germ-plasm) is the bearer? This function cannot 
be discharged by that portion of the germ-plasm of the ovum 
which has become converted into the somato-plasm (!) of the 
embryo, for the simple reason that tt has ceased to be germ-plasi, 
and must therefore have lost the properties characteristic of that 
substance. Neither can it be discharged by that portion of the 
germ-plasm of the ovum which is aggregated in the germ-cells 
of the embryo, for under these circumstances it is withdrawn 
from all direct relation with the developing somatic-cells. The 
question remains without an answer.” I believe myself to have 
answered this above. I do not recognize the somato-plasm of 
Professor Vines; my germ-plasm, or idio-plasm of the first 
ontogenetic grade, is not modified into the somato-plasm of 
Professor Vines, but into idio-plasm of the second, third, fourth, 
hundredth, &c. grade, and every one impresses its character on 
the cell containing it. 


It may be dullness, but I confess that this does not 
appear to me an “answer” to Professor Vines’ criticism. 
Even though “idio-plasm of the first ontogenetic grade” 
has to become “idio-plasm of the second, third, fourth, 
hundredth, &c. grade,” before in each of the grades con- 
cerned it can give origin to the somatic-cells which are 
distinctive of that grade, I cannot see that it makes any 
difference (in relation to Vines’ criticism) whether we speak 
of those cells as containing “somato-plasm,” or as con- 


Appendix TI, 189 


taining “somatic idio-plasm” of such and such a grade, 
plus “cytoplasm.” For whether we thus follow Weismann’s 
earlier terminology or his later, we are so far speaking 
about exactly the same thing, namely, the transformation of 
“oerm-plasm” into all the constituent cells of the “soma.” 
The difficulty is, in Vines’ words above cited, “to con- 
ceive that the germ-plasm of the ovum can impress upon 
the somato-plasm of the developing embryo the hereditary 
characters of which it (the germ-plasm) is the bearer” ; 
and Weismann says that this difficulty, which he acknow- 
ledges, can now be answered by substituting for his 
original statement that ‘“‘germ-plasm” becomes changed 
into “somato-plasm,” the statement that it is “idio-plasm” 
derived from “germ-plasm” which thus “impresses _ its 
character on the cell containing it.” But, “as a matter 
of logical accuracy,” there is surely here a distinction 
without a difference. For what is the difference between 
saying that germ-plasm “impresses” its character on the 
contents of a// somatic cells considered collectively under 
the term “somato-plasm,” and saying that every “onto- 
genetic grade” of germ-plasm ‘impresses’ z/s character 
on each successive group of somatic cells considered sever- 
ally under the term “idio-plasm” o: such and such a 
erade? At best this newer terminology has reference 
merely to a superadded hypothesis touching the mode— 
or rather the Azsfory—of the transition in question: it 
does not affect the original and essential doctrine of the 
transition itself. 


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Fk PLP AD NEI B A C 7 1 


ON TELEGONY. 


A wibELy different view, however, is taken by Mr. Herbert 
Spencer with regard to the theoretical interpretation of tele- 
gony. This, indeed, is precisely the opposite view to the 
one which is given in the text. For while I agree with 
Professor Weismann in holding that the facts of telegony 
(supposing them to be facts) are as compatible with the 
theory of germ-plasm as with that of gemmules, “ physio- 
logical units,” or any other theory which postulates a centri- 
petal flow of the carriers of heredity from somatic-cells to 
germ-cells, Mr. Spencer is of the opinion that these facts are 
destructive of any theory which postulates a continuity in the 
substance of heredity—1i. e., a centrifugal flow of the carriers 
of heredity. And, unquestionably, Mr. Spencer’s view is the 
prevalent one. Therefore, seeing that his opinion is not 
only of weight fer se, but is shared by the scientific world in 
general, I will here transcribe a somewhat lengthy discussion 
which I have recently held with him upon the subject. 

In the Contemporary Review for March, Mr. Spencer wrote 
as follows :— 


We pass now to evidence not much known in the world at 
large, but widely known in the biological world, though known 
in so incomplete a manner as to be undervalued in it. Indeed, 
when I name it probably many will vent a mental pooh-pooh. 
The fact to which I refer is one of which record is preserved 


192 An Examination of Wetsmanuism. 


in the museum of the College of Surgeons, in the shape oi 
paintings of a foal borne by a mare not quite thoroughbred, 
to a sire which was thoroughbred—a foal which bears the 
markings of the quagga. The history of this remarkable foal 
is given by the Earl of Morton, F.R.S., in a letter to the Presi- 
dent of the Royal Society (read November 23, 1820). In it he 
states that wishing to domesticate the quagga, and having 
obtained a male, but not a female, he made an experiment. 


I tried to breed from the male quagga and a youn, chestnut mare of 
seven-eighths Arabian blood, and which had never been bred from; the 
result was the production of a female hybrid, now five years old, and 
bearing, both in her form and in her colour, very decided indications of 
her mixed origin. I subsequently parted with the seven-eighths Arabian 
mare to Sir Gore Ouseley. who has bred from her by a very fine black 
Arabian horse. I yesterday morning examined the produce, namely, 
a two-year-old filly and a year-old colt. They have the character of the 
Arabian breed as decidedly as can be expected, where fifteen-sixteenths 
of the blood are Arabian; and they are fine specimens of that breed; 
but both in their colour and in the hair of their manes they have 
a striking resemblance to the quagga. Their colour is bay, marked 
more or less like the quagga in a darker tint. Both are distinguished 
by the dark line along the ridge of the back, the dark stripes across the 
fore-hand, and the dark bars across the back part of the legs}. 


Lord Morton then names sundry further correspondences. 
Dr. Wollaston, at that time President of the Royal Society, 
who had seen the animals, testified to the correctness of his 
description, and, as shown by his remarks, entertained no 
doubt about the alleged facts. But good reason for doubt 
may be assigned. There naturally arises the question—How 
does it happen that parallel results are not observed in other 
cases? If in any progeny certain traits not belonging to the 
sire, but belonging to a sire of preceding progeny, are re- 
produced, how is it that such anomalously-inherited traits are 
not observed in domestic animals, and indeed in mankind? 
How is it that the children of a widow by a second husband do 
not bear traceable resemblances of the first husband? To these 
questions nothing like satisfactory replies seem forthcoming ; 


+ «Pnilosophical Transactions of the Royal Society for the Year 1821,’ 
Part I. pp, 20-24. 


Appendix SLT. 193 


and, in the absence of replies, scepticism, if not disbelief, 
may be held reasonable. 

There is an explanation, however. Forty years ago I made 
acquaintance with a fact which impressed me by its significant 
implications ; and has, for this reason I suppose, remained in my 
memory. It is set forth in the Journal of the Royal Agricul- 
tural Society, vol. xiv. (1853), pp. 214 et seq., and concerns 
certain results of crossing English and French breeds of sheep. 
The writer of the translated paper, M. Malingié-Nouel, Director 
of the Agricultural School of La Charmoise, states that when 
the French breeds of sheep (in which were included ‘the 
mongrel Merinos’’) were crossed with an English breed, “the 
lambs present the following results. Most of them resemble the 
mother more than the father ; some show no trace of the father.” 
Joining the admission respecting the mongrels with the facts 
subsequently stated, it is tolerably clear that the cases in which 
the lambs bore no traces of the father were cases in which the 
mother was of pure breed. Speaking of the results of these 
crossings in the second generation ‘‘ having seventy-five per cent. 
of English blood,’ M. Nouel says :—‘‘ The lambs thrive, wear 
a beautiful appearance, and complete the joy of the breeder.... 
No sooner are the lambs weaned than their strength, their 
vigour, and their beauty begin to decay.... At last the con- 
stitution gives way...he remains stunted for life”: the 
constitution being thus proved unstable or unadapted to the 
requirements. How, then, did M. Nouel succeed in obtaining 
a desirable combination of a fine English breed with the rela- 
tively poor French breeds? 


He took an animal from “ flocks originally sprung from a mixture of 
the two distinct races that are established in these two provinces 
[Berry and La Sologne],” and these he “united with animals of another 


mixed breed . . . which blended the Tourangelle and native Merino 
blood of” La Beauce and Touraine, and obtained a mixture of all four 
races “ without decided character, without fixity, . . . but possessing the 


advantage of being used to our climate and management.” 
Putting one of these “ mixed-blood ewes to a pure New-Kent ram 
. . one obtains a lamb containing fifty-hundredths of the purest and 
most ancient English blood, with twelve and a-half hundredths of four 
different French races, which are individually lost in the preponderance 
of English blood, and disappear almost entirely, leaving the improving 


O 


194 An Examination of Wetsmannism. 


type in the ascendant. . . . All the lambs produced strikingly resembled 
each other, and even Englishmen took them for animals of their own 
country.” 


M. Nouel goes on toremark that when this derived breed was 
bred with itself, the marks of the French breeds were lost. 
“Some slight traces could be detected by experts, but these 
soon disappeared.” 

Thus we get proof that relatively pure constitutions pre- 
dominate in progeny over much mixed constitutions. The 
reason is not difficult to see. Every organism tends to become 
adapted to its conditions of life; and all the structures of 
a species, accustomed through multitudinous generations to the 
climate, food, and various influences of its locality, are moulded 
into harmonious co-operation favourable to life in that locality : 
the result being that in the development of each young indi- 
vidual, the tendencies conspire to produce the fit organization. 
It is otherwise when the species is removed to a habitat of 
different character, or when it is of mixed breed. In the one 
case its organs, partially out of harmony with the requirements 
of its new life, become partially out of harmony with one another ; 
since, while one influence, say of climate, is but little changed, 
another influence, say of food, is much changed; and, con- 
sequently, the perturbed relations of the organs interfere with 
their original stable equilibrium. Still more in the other case is 
there a disturbance of equilibrium. In a mongrel the constitu- 
tion derived from each source repeats itself as far as possible. 
Hence a conflict of tendencies to evolve two structures more or 
less unlike. The tendencies do not harmoniously conspire; 
but produce partially incongruous sets of organs. And evidently 
where the breed is one in which there are united the traits of 
various lines of ancestry, there results an organization so full of 
small incongruities of structure and action, that it has a much- 
diminished power of maintaining its balance; and while it 
cannot withstand so well adverse influences, it cannot so well 
hold its own in the offspring. Concerning parents of pure and 
mixed breeds respectively, severally tending to reproduce their 
own structures in progeny, we may therefore say, figuratively, 
that the house divided against itself cannot withstand the house 
of which the members are in concord. 


Appendix LT. 195 


Now if this is shown to be the case with breeds the purest of 
which have been adapted to their habitats and modes of life 
during some few hundred years only, what shall we say when the 
question is of a breed which has had a constant mode of life in 
the same locality for ten thousand years or more, like the quagga? 
In this the stability of constitution must be such as no domestic 
animal can approach. Relatively stable as may have been the 
constitutions of Lord Morton’s horses, as compared with the 
constitutions of ordinary horses, yet, since Arab horses, even in 
their native country, have probably in the course of successive 
conquests and migrations of tribes become more or less mixed, 
and since they have been subject to the conditions of domestic 
life, differing much from the conditions of their original wild life, 
and since the English breed has undergone the perturbing 
effects of change from the climate and food of the East to the 
climate and food of the West, the organizations of the horse and 
mare in question could have had nothing like that perfect balance 
produced in the quagga by a hundred centuries of harmonious 
co-operation. Hence the result. And hence at the same time 
the interpretation of the fact that analogous phenomena are not 
perceived among domestic animals, or among ourselves ; since 
both have relatively mixed, and generally extremely mixed, con- 
stitutions, which, as we see in ourselves, have been made 
generation after generation, not by the formation of a mean 
between two parents, but by the jumbling of traits of the one 
with traits of the other, until there exist no such conspiring 
tendencies among the parts as cause repetition of combined 
details of structure in posterity. 

Expectation that scepticism might be felt respecting this 
alleged anomaly presented by the quagga-marked foal, had led 
me to think over the matter; and I had reached this inter- 
pretation before sending to the College of Surgeons Museum 
(being unable to go myself) to obtain the particulars and refer to 
the records. When there was brought to me a copy of the 
account as set forth in the “ Philosophical Transactions,” it was 
joined with the information that there existed an appended 
account of pigs, in which a parallel fact had been observed. 
To my immediate inquiry—“ Was the male a wild pig ?”—there 
came the reply: “I did not observe.” Of course I forthwith 

O 2 


196 An Examination of Wersmanntsm. 


obtained the volume, and there found what I expected. It 
was contained in a paper communicated by Dr. Wollaston from 
Daniel Giles, Esq., concerning his ‘‘ sow and her produce,” which 
said that 


she was one of a well-known black and white breed of Mr, Western, 
the Member for Essex. About ten years since I put her to a boar of the 
wild breed, and of a deep chestnut colour, which I had just received 
from Hatfield House, and which was soon afterwards drowned by 
accident. The pigs produced (which were her first litter) partook in 
appearance of both boar and sow, but in some the chestnut colour of the 
boar strongly prevailed. 

The sow was afterwards put to a boar of Mr. Western’s breed (the 
wild boar having been long dead). The produce was a litter of pigs 
some of which, we observed with much surprise, to be stained and 
clearly marked with the chestnut colour which had prevailed in the 
former litter. 


Mr. Giles adds that in a second litter of pigs, the father of which 
was of Mr. Western’s breed, he and his bailiff believe there was 
a recurrence, in some, of the chestnut colour, but admits that 
their “recollection is much less perfect than I wish it to be.” 
He also adds that, in the course of many years’ experience, he 
had never known the least Ny geenceara of the chestnut colour in 
Mr. Western’s breed. 

What are the probabilities that these two anomalous results 
should have arisen, under these exceptional conditions, as 
a matter of chance? Evidently the probabilities against such 
a coincidence are enormous. The testimony is in both cases 
so good that, even apart from the coincidence, it would be 
unreasonable to reject it; but the coincidence makes accept- 
ance of it imperative. There is mutual verification, at the 
same time that there is a joint interpretation yielded of the 
strange phenomenon, and of its non-occurrence under ordinary 
circumstances. 

And now, in the presence of these facts, what are we to say? 
Simply that they are fatal to Weismann’s hypothesis. They 
show that there is none of the alleged independence of the 
reproductive cells; but that the two sets of cells are in close 
communion. They prove that while the reproductive cells 
multiply and arrange themselves during the evolution of the 


Appendix IT, 197 


embryo, some of their germ-plasm passes into the mass of 
somatic-cells constituting the parental body, and becomes 
a permanent component of it. Further, they necessitate the 
inference that this introduced germ-plasm, everywhere diffused, 
is some of it included in the reproductive cells, subsequently 
formed. And if we thus get a demonstration that the some- 
what different units of a foreign germ-plasm permeating the 
organism, permeate also the subsequently-formed reproductive 
cells, and affect the structures of the individuals arising from 
them, the implication is that the like happens with those native 
units which have been made somewhat diffezent by modified 
functions ; there must be a tendency to inheritance of acquired 
characters. 


My reply to this appeared in the April issue of the Contem- 
porary Review, as follows :-— 


Influence on Progeny of a Previous Stre. 


This is the last of the arguments which Mr. Spencer advances 
against the position of Professor Weismann. Alluding to the 
case of Lord Morton’s mare, he represents that the phenomenon 
which it serves so well to illustrate—viz., the influence of 
a previous sire on the progeny of another by the same dam—is 
hopelessly at variance with the theory of germ-plasm. I cannot 
quite gather the explanation which he would give of this 
phenomenon, further than that in some way or another it 
betokens an immediate influence of the hereditary material of 
the male on the body-tissues (‘‘ somatic cells”) of the female. 
And this is the view which is taken of the phenomenon by the 
Lamarckians in general. Yet, if we consider all that such an 
explanation involves, we shall find that it is a highly complex 
explanation, for it involves the following chain of hypotheses :— 
The first impregnation affects many, if not all, the somatic 
tissues of the mother by the germinal matter of the father; 
these tissues, in their turn, re-act on the maturing ova; this 
action and reaction is such that when one of the ova is after- 
wards fertilized by a different sire, the resulting offspring more 


198 An Examination of Wersmanntism. 


or less resemble the preceding sire. Unfortunately, neither 
Weismann himself nor any of his followers, as far as I know, 
has hitherto published an opinion on the subject; but I imagine 
that his answer would be three-fold. First, he may question 
the fact. Secondly, even admitting the fact, he may say it 
is much more easy to explain it by supposing that the germ- 
plasm of the first sire has in some way or another become 
partly commingled with that of the immature ova, as well as 
with that of the mature one which it actually fertilizes; and, if 
so, it would naturally assert its influence on the progeny of 
a subsequent sire. Millions of spermatozoa must have been 
playing around the ovaries after the first copulation, and only 
one of them was needed to fertilize the mature ovum. It is not 
necessary to suppose that some of the others succeeded in 
penetrating any of the immature ova, while these were still 
embedded in the substance of their ovaries. It may be that the 
life of “ids” is not commensurate with that of their containing 
spermatozoa. After the latter have perished and disintegrated, 
their ids may escape in thousands of millions, bathing in 
a dormant state the whole surfaces of both ovaries. And, if so, 
it is conceivable that when subsequent ova mature—i.e., come 
to the surface of their ovaries and rupture their follicles—these 
dormant ids adhere to their porous walls, through which they 
may pass. This may not seem a very probable explanation ; 
but, at any rate, it is a less improbable one than that on which 
the Neo-Lamarckians would found an argument against the 
continuity of germ-plasm. For,— 

Thirdly, is it not literally inconceivable that this Neo- 
Lamarckian explanation can be the true one? Can it be 
seriously contemplated that there is any such mechanism as the 
explanation must needs assume? If it is difficult to accept such 
a machinery as is supposed by the theory of pangenesis, whereby 
every cell in the body casts off “gemmules,” which are the 
carriers of heredity from their respective tissues to the germinal 
elements, what are we to say of such a machinery as the 
following :—A machinery which distributes through the body of 
a female gemmules from the disintegrated spermatozoa of her 
mate; which distributes them se/ectzvely, so that they shall 
all eventually lodge in those tissue-cells of the female which 


Appendix IT, 199 


correspond, part for part, with the tissue-cells of the male from 
which they were originally derived; which then insures that 
when a gemmule has thus reached its appropriate cell in the 
female body, it will thereupon modify the pre-existing gemmules 
in that cell, so that when they are shed and go to form the 
germinal contents of future ova, they endow the latter with the 
hereditary qualities of the male in question ? 

Such, it seems to me, is a fair statement of the whole case up 
to date. But I think it may be apposite now to publish the 
main results of an inquiry on which I have been engaged for the 
last three years. 

First as to the facts. The investigations have been pursued 
on three different lines: (1) I raised discussions on the subject 
in the principal breeders’ and fanciers’ journals of this country, 
and also of America. (2) I entered into private correspondence 
with contributors of the largest experience, and also with pro- 
fessional and amateur breeders, fanciers, &c., who addressed me 
directly on the subject. (3) I started experiments with the 
varieties which these inquiries indicated as most likely to 
yield positive results. At present nothing need be said with 
regard to these experiments, because they are not sufficiently 
matured. But it is desirable to state the general upshot of 
the correspondence. 

The principal result is to show that the phenomenon is of 
much less frequent occurrence than is generally supposed. 
Indeed, it is so rare that I doubt whether it takes place in more 
than one or two per cent. of cases. I must add, however, that 
nearly all my professional correspondents would deem this an 
absurdly low estimate. Most of them are quite persuaded that 
it is of frequent occurrence, many of them regard it as a general 
rule, while some of them go so far as to make a point of always 
putting a mare, a bitch, &c. to a good pedigree male in her first 
season, so that her subsequent progenies may be benefited by 
his influence, even though they be engendered by inferior sires. 
But I am certain that these estimates must be largely discounted 
in view of merely accidental resemblances, and still more on 
account of the prevalent belief upon the subject, which, where 
unquestioningly entertained, prevents anything like a critical 
estimate being formed. 


200 Anz Examination of Wetsmannism. 


But that the phenomenon does occur in some small percentage 
of cases there can be no reasonable doubt—as a result, I mean, 
of analysing the hundreds of cases which have now been sub- 
mitted to me, especially with regard to dogs. One thoroughly 
well observed case occurring among pedigree animals is worth 
any number of slipshod statements, when precedent belief, in- 
efficient isolation, exaggeration of memory, and so forth, have to 
be allowed for. On the present occasion space does not admit 
of giving such special instances, so I must ask it to be taken 
for granted that my evidence is enough to prove the fact of a 
previous sire asserting his influence on a subsequent progeny, 
although this fact is one of comparatively rare occurrence. It 
may be added that I have failed to find any good evidence of 
its ever occurring at allin the case of man. For although I have 
met with an alleged instance of a white woman, who, after having 
borne children to a negro husband, had a second family to a 
white one, in which some negro characteristics appeared, I have 
not been able to mect with any corroboration of this instance. 
I have made inquiries among medical men in the Southern 
States of America, where in the days of slavery it was frequently 
the custom that young negresses should bear their first children 
to their masters, and their subsequent chiidren to negro hus- 
bands; but it never seems to have been observed, according to 
my correspondents, that these subsequent children were other 
than pure negroes. Such, however, was not the same case as the 
one above mentioned, but a reciprocal case; and this may have 
made a difference. If any reader should happen to know of 
another instance where a negro was the first husband, I hope he 
will inform me as to the result. 

It has hitherto puzzled me why the phenomenon in question, 
since it does certainly occur in some cases, should occur so rarely 
as the above inquiries prove. But I think that Mr. Spencer’s 
suggestion on this point is a valuable one, as it seems to 
present an excellent promise of solving the puzzle. 

This suggestion, it will be remembered, is that when the first 
sire is of a relatively stable and also of a markedly different 
ancestral stock from the dam—e.g., of a different species, as in 
the case of Lord Morton’s mare—there will be most likelihood of 
his impressing his ancestral characters on the progeny of the 


Appendix LI. 201 


second sire’. And, as he remarks, it would indeed be an 
extraordinary coincidence if both the well-authenticated cases 
given in the College of Surgeons Catalogue should have con- 
formed to his explanation by mere accident. To which I may 
add that the supposition of such an accidental coincidence would 
seem to be virtually excluded by the recent occurrence of yet 
a third case of exactly the same kind. This took place in the 
Zoological Gardens, where a wild ass of one species was the 
previous sire to a foal born of another species: the subsequent 
sire was of the same species as the mother, and his foal, born 
a few months ago, presented an unmistakable resemblance to 
the other species. A brief account of the particulars is given 
by Mr. Tegetmeier in the /ze/d for December 14, 1892. 

So much, then, for the facts. As regards their interpretation, 
it certainly seems to me that the one which I have supposed to 
be given by Weismann is less difficult of acceptance than the 
one which is given by the Lamarckians, as we have seen above. 
But it also seems to me that the latter explanation is not the oniy 
one available under the Lamarckian hypothesis. For, even 
under this hypothesis, there is no need to assume that the in- 
fluence of the first sire is exerted on all the somatic tissues 
of the mother, and that these again reflect this influence on 
the ovum which is afterwards fertilized by the second sire. 
A mechanism that could effect all this may well be deemed im- 
possible. But a much simpler explanation can be furnished 
by the Neo-Lamarckians, on lines similar to those upon which 
I have supposed that Weismann’s explanation would run. For, 
on their common supposition that the substance of heredity is 
particulate, it matters not in the present connexion whether we 
suppose the particles to be ids or gemmules. Indeed, it is more 
in accordance with the hypothetical endowments of the latter 
than of the former, that they should be capable of penetrating 
the coats of an ovum, if they can survive the disintegration of 
their containing spermatozoén. Nevertheless, thus far it does 
not seem to me that any theory belonging to the family of pan- 
genesis can gain any advantage over the theory of germ-plasm, 


* Readers who may happen to be acquainted with De Vries’ impoitant 
essay on heredity will perceive how well this suggestion fits in with his 
_ modification of Pangenesis. 


202 An Examination of Wersmannism. 


by appealing to the fact of a previous sire sometimes affecting 
the progeny of a subsequent one. The case, however, is widely 
different if we turn from animals to plants, thus. 

The advantage which any theory of gemmules seeks to gain 
over the theory of germ-plasm by an appeal to the fact in ques- 
tion, consists in supposing that the influence of the previous sire 
is exercised in the first instance on the somatic cells of the female. 
For this would prove that the germinal elements of the male are 
capable of communicating their hereditary qualities, not only 
by mixing with the germinal elements of the female (as in 
ordinary fertilization) but also by direct contact with the general 
tissues of the female. And this again would prove that the 
fundamental postulate of the theory of germ-plasm is erroneous 
—i.e., the postulate of the continuity of germ-plasm, or of its 
perpetual restriction to a “sphere” of its own. This, as all who 
are acquainted with the literature of the subject will at once 
perceive, would be a serious blow to the whole Weismannian 
system. But, as we have seen, the current Lamarckian inter- 
pretation of the fact in question involves the supposition of 
a physiological machinery so inconceivably complex that instead 
of serving to corroborate the theory of gemmules (or of physio- 
logical units) it would go to render that theory incredible’. 


' As already indicated, I cannot gather from his remarks on the subject 
which, if any, of the alternative interpretations of the phenomena that 
we are considering Mr. Spencer adopts. From the following sentences 
it would appear that he assigns yet a third interpretation, and this as the 
only possible one. For he says of these phenomena: ‘They prove 
that while the reproductive cells multiply and arrange themselves 
during the evolution of the embryo, some of their germ-plasm passes 
into the mass of somatic cells constituting the parental body, and 
becomes a permanent component of it. Further, they necessitate the 
inference that this introduced germ-plasm, everywhere diffused, is some 
of it included in the reproductive cells subsequently formed ” (Contem- 
porary Review, March, p. 452). This appears to mean that the 
influence of a previous sire can only be explained by supposing that the 
developing embryo inoculates the somatic tissues of its mother with 
hereditary material derived from its father, and that the maternal tissue 
afterwards reflect some of this material (or its influence) to the still 
unripe ovarian ova. If this be the hypothesis intended, it seems to me 
more complex than any of the three which I have suggested. But, be 
this as it may, we certainly cannot agree that such an hypothesis 


Appendix LT, 203 


If, however, we turn to plants, we find a considerable number 
of facts which unquestionably demonstrate the only point which 
this interpretation has been adduced to suggest. For these 
facts show that, in not a few cases, the germinal matter of 
pollen-grains is capable of asserting its influence beyond the 
ovules to the somatic tissues of the ovary, and even to the flower- 
stalk of the mother plant. Here, then, we have simple and con- 
clusive evidence of the material of heredity exercising a direct 
influence on somatic tissues. How this well-known fact is to be 
met by the theory of germ-plasm is a question which does not 
seem to have thus far engaged the attention of Professor Weis- 
mann, or of any of his followers. For particulars touching this 
phenomenon, so highly important in its relation to the theory 
of germ-plasm, I cannot do better than refer to the eleventh 
chapter of Darwin’s work on the “ Variation of Animals and 
Plants under Domestication.” 


Again, in the Contemporary Review for May, Mr. Spencer 
WIOlG.s—4 


In the essay to which this is a postscript, conclusions were 
drawn from the remarkable case of the horse and quagga there 
narrated, along with an analogous case observed among pigs. 
These conclusions have since been confirmed. I am much 
indebted to a distinguished correspondent who has drawn my 
attention to verifying facts furnished by the offspring of whites 
and negroes in the United States. Referring to information 
given him many years ago, he says :—“ It was to the effect that 
the children of white women by a white father had been ve- 
peatedly observed to show traces of black blood, in cases when 
the woman had previous connexion with [i.e., a child by] a negro.” 
At the time I received this information, an American was 
visiting me; and, on being appealed to, answered that in the 
United States there was an established belief to this effect. 
Not wishing, however, to depend upon hearsay, I at once wrote 
to America to make inquiries. Professor Cope of Philadelphia 
has written to friends in the South, but has not yet sent me the 


is ‘‘ proved” by the facts, or that the latter ‘‘necessitate ” the inference 
as to its being some of the emdryo’s germinal matter which enters the 
unripe ova. 


204 An Examination of Wetsmannism. 


results. Professor Marsh, the distinguished paleontologist, of 
Yale, New Haven, who is also collecting evidence, sends 
a preliminary letter in which he says:—“I do not myself know 
of such a case, but have heard many statements that make their 
existence probable. One instance, in Connecticut, is vouched 
for so strongly by an acquaintance of mine, that I have good 
reason to believe it to be authentic.” 

That cases of the kind should not be frequently seen in the 
North, especially nowadays, is of course to be expected. The 
first of the above quotations refers to facts observed in the South 
during slavery days; and, even then, the implied conditions 
were naturally very infrequent. Dr. W. J. Youmans of New York 
has, on my behalf, interviewed several medical professors, who, 
though they have not themselves met with instances, say that 
the alleged result, described above, “is generally accepted as 
a fact.’ But he gives me what I think must be regarded as 
authoritative testimony. It is a quotation from the standard 
work of Professor Austin Flint, and runs as follows :— 


A peculiar and, it seems to me, an inexplicable fact is, that previous 
pregnancies have an influence upon offspring. This is well known to 
breeders of animals. If pure-blooded mares or bitches have been once 
cevered by an inferior male, in subsequent fecundations the young are 
likely to partake of the character of the first male, even if they be after- 
wards bred with males of unimpeachable pedigree. What the mechanism 
of the influence of the first conception is, it is impossible to say; but the 
fact is incontestable. ‘The same influence is observed in the human 
subject. A woman may have, by a second husband, children who 
resemble a former husband, and this is particularly well marked in 
certain instances by the colour of the hair and eyes A white woman 
who has had children by a negro may subsequently bear children to 
a white man, these children presenting some of the unmistakable peculi- 
arities of the negro race!. 


Dr. Youmans called on Professor Flint, who remembered 
“investigating the subject at the time his larger work was 
written [the above is from an abridgment], and said that he 
had never heard the statement questioned.” 

Some days before I received this letter and its contained 


*«A Text Book of Human Physiology.” By Austin Flint, M.D., LL. D. 
Fourth edition. New York: D. Appleton & Co, 1888. Page 797. 


Appendix 11, 205 


quotation, the rem mbrance of a remark I heard many years 
ago concerning dogs, led to the inquiry whether they furnished 
analogous evidence. It occurred to me that a friend who is 
frequently appointed judge of animals at agricultural shows, 
Mr. Fookes, of Fairfield, Pewsey, Wiltshire, might know some- 
thing about the matter. A letter to him brought various 
confirmatory statements. From one ‘who had bred dogs for 
many years” he learnt that— 

It is a well-known and admitted fact that if a bitch has two litters 
by two different dogs, the character of the first father is sure to be 
perpetuated in any litters she may afterwards have, no matter how 
pure-bred a dog may be the begetter. 


After citing this testimony, Mr. Fookes goes on to give illustra- 
tions known to himself. 


A friend of mine near this had a very valuable Dachshund bitch, 
which most unfortunately had a litter by a stray sheep-dog The next 
year her owner sent her on a visit to a pure Dachshund dog, but the 
produce took quite as much of the first father as the second, and the 
next year he sent her to another Duchshund with the same result. 
Another case:—A friend of mine in Devizes had a litter of puppies, 
unsought for, by a setter from a favourite pointer bitch, and after this 
she never bred any true pointers, no matter of what the paternity was. 


These further evidences, to which Mr. Fookes has since 
added others, render the general conclusion incontestable. 
Coming from remote places, from those who have no theory to 
support, and who are some of them astonished by the unexpected 
phenomena, the agreement dissipates all doubt. In four kinds 
of mammals, widely divergent in their natures—man, horse, dog, 
and pig—we have this same seemingly anomalous kind of 
heredity made visible under analogous conditions. We must 
take it as a demonsirated fact that, during gestation, traits 
of constitution inherited from the father produce effects upon 
the constitution of the mother; and that these communicated 
effects are transmitted by her to subsequent offspring. We are 
supplied with an absolute disproof of Professor Weismann’s 
doctrine that the reproductive cells are independent of, and 
uninfluenced by, the somatic cells; and there disappears abso- 
lutely the alleged obstacle to the transmission of acquired 
characters... . 


206 An Examination of Wetsmannism. 


There is one other passage in Dr. Romanes’ criticism—that 
concerning the influence of a previous sire on progeny—which 
calls for comment. He sets down what he supposes Weismann 
will say in response to my argument. ‘“ First, he may question 
the fact.” Well, after the additional evidence given above, 
I think he is not likely to do that; unless, indeed, it be that 
along with readiness to base conclusions on things “it is easy 
to imagine” there goes reluctance to accept testimony which it 
is difficult to doubt. Second, he is supposed to reply that ‘the 
germ-plasm of the first sire has in some way or another become 
partly commingled with that of the immature ova”; and 
Dr. Romanes goes on to describe how there may be millions 
of spermatozoa and “thousands of millions ” of their contained 
“ids” around the ovaries, to which these secondary effects are 
due. But, on the one hand, he does not explain why in such 
case each subsequent ovum, as it becomes matured, is not 
fertilized by the sperm-cells present, or their contained germ- 
plasm, rendering all subsequent fecundations neediess; and, on 
the other hand, he does not explain why, if this does not happen, 
the potency of this remaining germ-plasm is nevertheless such 
as to affect not only the next succeeding offspring, but all 
subsequent offspring. The irreconcilability of these two impli- 
cations would, I think, sufficiently dispose of the supposition, 
even had we not daily multitudinous proof that the surface of a 
mammalian ovarium is not a sperm-atheca. The third difficulty 
Dr. Romanes urges is the inconceivability of the process by 
which the germ-plasm of a preceding male parent affects the 
constitution of the female and her subsequent offspring. In 
response, I have to ask why he piles up a mountain of 
difficulties based on the assumption that Mr. Darwin’s 
explanation of heredity by “ Pangenesis” is the only available 
explanation preceding that of Weismann? and why he presents 
these difficulties to me more especially, deliberately ignoring 
my own hypothesis of physiological units? It cannot be that 
he is ignorant of this hypothesis, since the work in which it is 
variously set forth (“Principles of Biology,” §§ 66-97) is one 
with which he is well acquainted: witness his ‘‘ Scientific 
Evidences of Organic Evolution”; and he has had recent 
reminders of it in Weismann’s “ Germ-plasm,” where it is 


Appendix IT, 207 


repeatedly referred to. Why, then, does he assume that 
I abandon my own hypothesis and adopt that of Darwin, there- 
by entangling myself in difficulties which my own hypothesis 
avoids? If, as I have argued, the germ-plasm consists of 
substantially similar units (having only those minute differences 
expressive of individual and ancestral differences of structure), 
none of the complicated requirements which Dr. Romanes 
emphasises exists, and the alleged inconceivability disappears. 


To this I responded, in the Contemporary Review for 
June :— 


With regard to the influence of a previous sire, I ventured 
in my article to show that, even supposing it to be a fact, 
the phenomena concerned would not constitute any valid 
evidence against Weismann’s theory of germ-p!asm, and, of 
course, still less would ‘‘they prove that while the reproductive 
cells multiply and arrange themselves during the evolution 
of the embryo, some of their germ-plasm passes into the mass 
of somatic cells constituting the parental body, and becomes 
a permanent component of it,” with the result that the phe- 
nomena in question ‘‘ are simply fatal to Weismann’s hypothesis.” 
For a much simpler and more probable explanation is to be 
found in supposing that the unused germ-plasm of the first sire 
may survive the disintegration of its containing spermatozoa in 
the Fallopian tubes of the female, and thus gain access to the 
hitherto unripe ova arectly, instead of first having to affect the 
whole maternal organism, and then being reflected from it to 
them. I showed, at some length, how immensely complex the 
mechanism of any such process would necessarily have to be; 
and for the purposes of exposition I employed the terminology 
of Darwin’s theory of Pangenesis. Mr. Spencer now says: 
“In response, I have to ask why he [I] piles up a mountain 
of difficulties based on the assumption that Mr. Darwin’s 
explanation of heredity by ‘ Pangenesis’ is the only available 
explanation preceding that of Weismann? and why he presents 
these difficulties to me more expecially, deliberately ignoring 
my own hypothesis of physiological units?” Now my answer 
to this is very simple. I do not hold a brief for Weismann. 
On the contrary, | am in large measure an opponent of his 


208 An Examination of Wersmannism. 


views; and my only object in publishing my previous article 
was to save the theory of use-inheritance from what seemed to 
me the weaker parts of Mr. Spencer’s advocacy, while thus all 
the more emphasizing my acceptance of its stronger parts. 
Therefore, the impression which he seems to have gained from 
my attempts at impartiality is entirely erroneous. Far from 
“deliberately ignoring” any of his arguments or hypotheses 
which seemed to me at all available on the side of use-inherit- 
ance, | everywhere endeavoured to make the most of them. 
And, as regards this particular instance, I expressly used the 
term “gemmules,’’ instead of ‘physiological units,’ simply 
because I could not see that, as far as my “mountain of dif- 
ficulties’ was concerned, it could make one atom of difference 
which term I employed. It now appears, however, that, in 
Mr. Spencer’s opinion, there is some very great difference. 
For, while he allows that the “mountain of difficulties” which 
I have “piled up” against his interpretation of the alleged 
phenomena would be valid on the supposition that the ultimate 
carriers of heredity are ‘‘ gemmules,” he denies that such is the 
case if we suppose these ultimate carriers to be “ physiological 
units.’ For this statement, however, he gives no justification ; 
and, as I am unable to conceive wherein the difference lies, 
I sincerely hope that in any subsequent editions of his pamphlet 
Mr. Spencer will furnish the requisite explanation. Gladly 
substituting the words ‘ physiological units” wherever I have - 
used the word “‘ gemmules,” I am genuinely anxious to ascertain 
how he would overcome the “mountain of difficulties” in 
question. For I do not regard the subject as one of mere 
dialectics. It is a subject of no small importance to the general 
issue, Weismann versus Lamarck ; and, therefore, if Mr. Spencer 
could show that the phenomena in question make exclusively in 
favour of the latter, as he alleges, he might profitably inform us 
in what way he supposes them to do so. 

In conclusion, I would like to take this opportunity of ex- 
plaining that my former article was written in Madeira, where 
I did not receive a copy of Weismann’s most recent work, 
entitled Zhe Germ-flasm, until the Contemporary Review for 
April was being printed off. Thus, I was not then aware that in 
this work Professor Weismann had fully anticipated several 


Appendix IT, 209 


of Mr. Spencer’s criticisms—including this matter of the 
influence of a previous sire. Here he adopts exactly the position 
which in my article I surmised that he would; so that, to all 
who have read Zhe Germ-flasm, it must have appeared that 
I was prophesying after the event. Hence the need of this 
explanation. 


Lastly, in the same issue of the Contemporary Review, 
M1. Spencer explained :— 


Mr. Darwin’s hypothesis of Pangenesis implies not only that 
the reproductive cell must contain numerous kinds of gemmules 
derived from different organs, but that the numbers of these 
gemmules must bear to one another something like the pro- 
yortions which the originating organs bear to one another in 
size. The conception involves many different £z7ds, whose 
numbers are in many different proportions, and I supposed the 
difficulty alleged was, that for the influence of a previous sire to 
be communicated from the growing foetus to the mother would 
imply not only the transfer of the various kinds of gemmules 
derived from him, but also maintenance of their numerical 
proportions, and that again these gemmules, diffused throughout 
the maternal system, would have to be transferred in these pro- 
portions to the subsequently formed ova. No such difficulties 
arise if the units conveying hereditary characters are of one 
kind only. 


From this it is apparent that Mr. Spencer has misunder- 
stood “ the difficulty alleged,” and that the desired explanation 
is not yet forthcoming. I did not say anything about “ kinds ” 
or “ proportions” of the carriers of heredity; my difficulty 
is to conceive of any mechanism whereby these carriers can 
first directly influence the somatic-cells of the mother, and 
then indirectly reflect this influence upon her germ-cells. 
Also, I cannot see any obvious necessity for the intervention 
of the “ embryo” in the process. 

















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Acquired characters.—Sce Somatogenetic characters. 

Amphigony (Hackel).—Sexual reproduction. 

Amphimixis (Weismann).—The mingling of the hereditary substances 
of two individuals in an act of sexual union. 

Ancestral germ-plasm.—See p. 123. 

Asexual Reproduction.—In which there is no liberation of special 
germ cells containing the potentiality of the adult organism, but 
in which the same object is effected by the liberation of buds, over- 
‘growths, &c., which develop into the parent form. There are 
many forms of asexual reproduction. 

Atavism.—The abnormal occurrence in existing species of characters 
which were peculiar to ancestral species, e.g., see Darwin and 
after Darwin, 2nd ed., Part I, p. 94. 

Biophore.—See p. 123. 

Blastogenetic characters.—See Plasmogenetic characters. 

Calyx.—The outermost covering of the flower, which protects it before 
opening. Its position and precise function vary. 

Cell nucleus.—A spherical or ovoid body embedded in the cell proto- 
plasm, which has important functions in cell division and in repro- 
duction. It consists of chromatin and achromatin. There are often 
several nuclei in one cell, whilst some cells have not been shown to 
have a nucleus at all. 

Cessation of Selection (Romanes).—S¢e Panm'xia. 

Chromatin threads.—Immediately before a cell divides the nucleus is 
resolved into chromatin fibres or threads and an achromatin matrix. 
These chromatin fibres are then marshalled into either rods or loops, 
&c., as the division of the cell proceeds (see Darwin and after 
Darwin, figs. 36, 37, and 38). Subsequent changes in the threads 
conclude the division (for a description of which consult the account 
above). 

Chromosomes.—See Chromatin threads, 


P2 


212 Glossary. 


Compositae.—Plants in which the inflorescence consists of numerous 
small flowers brought together into a dense head, the base of which 
is enclosed by a common envelope (e. g. the Daisy, Dandelion, &c.). 

Congenital characters.—Sce Plasmogenetic characters. 

Conjugation.—This term is applied to a process observed in the 
Protozoa (q. v.), which seems to correspond to the sexual reproduction 
of the Metazoa (q.v.). The majority of the Protozoa cannot long 
continue to reproduce themselves asexually without becoming 
degenerate, or rather without becoming altogether extinct. Two 
individuals (as a rule) consequently unite either temporarily or 
permanently. In the former case, an exchange of material is effected ; 
and in the latter, complete fusion takes place. 

Correlation.—The normal coincidence of one phenomenon, character, 
&c., with another. 

Cytoplasm.—See pp. 30 and 32. 

Determinant.—See p. 123. 

Ectoblast.—Syn. of epiblast and ectoderm. The general result of the 
division of a fertilized ovum is a two-layered ball of cells (a gastrula). 
The outer layer is called the ectoblist and the inner layer the ento- 
blast. (See Darwin and after Darwin, p. 137 et seq.). 

Embryology.—Hence embryogenesis, &c. The study of the develop- 
ment or the early growth of the individual. 

Entoblast.—Syn. of hypoblast and endoderm. See Ectoblast. 

Epigenesis (Harvey).—The theory that organisms are formed by the 
development of the egg itself, and not by the expansion of a miniature 
within the egg (preformation). 

Fallopian Tubes.—The tubes through which the spermatozoa pass to 
effect fertilization, and through which the ova pass from the ovary to 
the uterus. 

Fission.—Syn. of fissiparous separation. The breaking into two 
(without karyokinesis—q.v.) of a cell, which has, by overgrowth, 
disturbed its physiological equilibrium. This process is almost 
mechanical. 

Formative material.—Sce p. 56. 

Gemmation.—That form of asexual reproduction known as budding. 

Gemmules (Darwin).—Minute granules, formed by the division of the 
general body-cells, which are supposed to be dispersed throughout the 
entire system. These themselves multiply by division, and are 
collected from all parts of the body to constitute the sexual 
elements. 

Germ-plasm.— See p. 32. 

Hydroids.— Belong to a division (Hydrozoa) of the stinging-animals 
or Coelenterata. They occur both in the sea and in fresh water, and 
are solely polypoid (i.e. tubular and tentacled). 


Glossary. 213 


Hydromedusae.—Also Hydrozoans. Hydroid colonies with special 
sexually reproductive persons, which are often liberated as floating 
bells or discs. 

Idio-plasm (A and B).— See pp. 31 and 32. 

Ids.—See p. 123. 

Invertebrata.—Animals with a dorsal heart and without a backbone. 

Karyokinesis.— The changes which are observed in the nucleus both 
immediately before and after cell division. See Chromatin threads. 

Lamarckian factors. See Somatogenetic characters. Also Neo- 
Lamarckians, 

Metaphyta.— Multicellular plants (q. v.). 

Metazoa.—Multicellular animals (q. v.). 

Micellae (Nageli).—See Molecules, with which they are identical. 

Microsomata.—The protoplasm of certain vegetable cells is in places 
characterized by the presence of minute corpuscles, which may be 
regarded as part of the protoplasm, and are certainly of a protoplasmic 
nature. These are termed Microsomata, 

Molecules (Weismann).— See p. 122. 

Multicellular organisms.—Organisms composed of many cells, as 
distinguished from the Unicellular organisms, where each individual 

. is constituted of only one cell. 

Natural Selection.—Survival of the Fittest in the struggle for 
existence. For a full account of the process see Darwin and after 
Darwin, p. 251 et seq. 

Neo-Darwinians.—Those who believe that Natural Selection has 
been the only modifying influence in the evolution of species, and 
that the material for its action has been only plasmogenetic 
characters (q. v.). 

Neo-Lamarckians.—Those who hold that organic evolution has been 
effected solely by means of the occurrence and preservation (inheritance) 
of somatogenetic characters (q. v.). 

Nuclear Thread or Loops.—See Chromatin threads. 

Nucleo-plasm.—See pp. 30 and 32. 

Nucleus.—See Cell nucleus. 

Nutritive congenital characters.—Sce p. 64. 

Ontogenetic grades.—See p. 35. 

Ontogeny.—The life history of the individual, as distinguished from the 
ancestral history of the race (Phylogeny). 

Ova.—Eggs—the product of the female reproductive gland (ovary or 
ovarium). 

Ovule.— The seed in its earliest condition, 

Pangenesis (Darwin).—The theory of Heredity by gemmules (q. v.). 

Panmixia (Weismann).—The condition ot free intercrossing, i.e. 
where Natural Selection (q. v.) cannot act. 


214 Glossary. 


Parthenogenesis.—A degenerate form of sexual reproduction, in which 
the egg develops without having been fertilized by the male 
element. 

Phylogeny.—The ancestral history of the race, as distinguished from 
the life history of the individual (Ontogeny). 

Physiological Units (Spencer).—Special units which it is inferred 
a plant or animal of any species is made up of, and in all of which 
dwells the intrinsic aptitude to aggregate into the form of that 
species. 

Plasma.—The constituent material of cells, e. g. germplasma (of sexual- 
cells), somatoplasma (of body-cells). 

Plasmogenetic characters.—Variations due to admixtures of germ- 
plasm in acts of sexual fertilization (and therefore present at birth), 
as distinguished from somatogenetic characters—variations which 
have been acquired independently of germ-plasm. See Somato- 
genetic characters. 

Polar bodies.—Before an egg is fertilized the nucleus moves towards 
the periphery and divides twice. The two cells that are thus 
formed are the polar bodies. The extrusion of polar bodies is 
probably universal among animals, but only one polar body is 
extruded from parthenogenetic ova. See Darwin and after Darwin, 
pp- 125 and 126. 

Preformation.—The old conjecture (1672—Malpighi) that the de- 
velopment of an embryo was merely the expansion or unfolding of 
a miniature of the adult within the egg. 

Protophyta.—Unicellular plants (q. v.). 

Protoplasm.—Living matter. 

Protozoa.—Unicellular animals (q. v.). 

Representative Congenital characters.— See p. 65. 

Reversion.—See Atavism. 

Rudimentary Organs.—Usually considered a synonym of the term 
“¢ vestigial characters,” and is the name under which are included all 
those organs which, either from having become uscless or from other 
causes, have been much reduced in size, e.g. the muscles of the 
external ear in man (see Darwin and after Darwin, p. 76), &c. 
Latterly the former expression has been used to describe organs in 
process of development (e.g. the electric organ of the skate—/oc. cit., 
p- 365 e¢ seg.’, whilst the latter is made to embrace all those organs 
in process of elimination. 

Soma.—A general term descriptive of the whole mass of the body-cells 
of an organism. 

Somatic-idio-plasm.—See p. 32. 

Somatogenetic characters.—Characters acguzred by the soma (i.e. 
variations acquired after birth by the action of the environment), as 


Glossary. 215 


distinguished from characters produced and potentially present from 
the first by a union of two masses of germ-plasm—plasmogenetic 
characters (q. v.). 

Somato-plasm.—See p. 32. 

Specialized congenital characters.—See p. 65. 

Spermathecae.— Organs for the storing of the seminal fluid received in 
copulation. 

Spermatogenesis.—The precise development of spermatozoa. 

Spermatozoa.—The essential elements in the male seminal fluid, and 
secreted by the testis—the male reproductive gland. 

Stirp (Galton).—See p. 58. 

Telegony.— See p. 141. 

Unicellular Organisms.—Organisms composed of a single cell only, 
as distinguished from those consisting of aggregations of cells— 
Multicellular organisms, 

Vertebrata.—Animals with a backbone and a ventral heart. 

Vestigial Organs.—See Rudimentary organs. 

Xenia.— See p. 141. 


JeNE Dae exe 


A. 


Acquired characters, definition of, 
p- 5; inheritance of, 6, 15, 49, 57, 
60, 67, 69, 71, 81, 83-84, 93- 
OO BACs BsIOy,) LiG-111,. 137, 
173, e¢ seg.; Galton on inheri- 
tance of, 62, 106. 

Adaptive development, Weismann 
on, 19. 

Algae, De Vries on the chromato- 
phores of, 83, 111. 

Amphigony, the cause of indi- 
vidual hereditary variation, 91, 
100-101, 

Amphimixis, see Sexual propaga- 
tion. 

Ancestral germ-plasm, 123. 

Atavism, 3, gI, 105, 


B. 


Bary, De, on Weismann’s theory, 
152. 

Basidiomycetes, go. 

Begonia, regeneration in, 4, 52. 

Biophores, 123. 

Body-cells, and germ-cells, 29. 

Brooks, theory of heredity, 2. 

Bud-variation, go, 94, 96, 98-99 ; 
Weismann on, 95, 97, 161; 
Fritz Miiller on, 95. 

Butterflies, climatic varieties of 
and Weismann’s theory, 67- 
68, 127-128. 


C. 


Candolle, De, on inheritance of 
acquired characters in plants, 93. 


‘Carriers of Heredity,” 32, 38, 
70, 78, 122. 


Cessation of Selection, see Pan- 
mixia. 

Chromatophores, of Algae,83, 111. 

Compositae, pollen of, 5. 

Congenital variations, definition 
Oipekcrinheritances Of,0-0:8 120i; 
sexual propagation the cause 
of, 11; Darwin on, 13; origin 
of, 23, 25, 100, 102; nutritive 
congenital changes, 64; exam- 
ples of, 64; specialized con- 
genital changes, 65 ; representa- 
tive congenital changes, 65 ; 
Galton on, 134. 

Continuity of germ-plasm, see 
Germ-plasm. 

Crustacea, and the inheritance of 
acquired characters, 94. 

Cuttings, and bud-variation, 98. 

Cytisus adam, grafting of, 127. 


D. 


Darwin, Charles,and Pangenesis, 
2, 26; arguments in favour of 
pangenesis, 3, 59; on the cause 
of congenital variations, 13 ; 
comparison of his theory of 
heredity with that of Weis- 
mann, 52, 55, 73) 92, I105- 
106, 115, 133, 173 éf seg.3.on 
germ and somatic-cells, 76; on 
the influence of pollen upon 
somatic tissues, 79-80; on graft- 
hybridization, 83; on bud- 
variation, 95 ; on the causes of 
variation, 102, 1613; on the 
inheritance of acquired charac- 
ters, 107, I11-112; on Xenia, 
144; On sexual union, 154. 


218 


Death, Weismann on the origin of, 
8, 10; in plants, Io. 

Determinants, 123. 

Direct action of environment, on 
unicellular organisms, 15, 23. 


E. 


Elsberg, theory of heredity, 2. 

Environment, direct action of on 
Protozoa, 15. 

Evolution, see Organic evolution. 


F, 


Flint, Prof. Austin,on Telegony, 
204. 

Focke, on Xenia, 141, 144. 

** Formative material,” and germ- 
plasm, 56. 

Fungi, Prof. Vines on Basidiomy- 
cetes, yo. 


G, 


Galton, Francis, theory of here- 
dity (stirp), 2; and Weismann’s, 
51, 58-59, 69, 73, 92, 105-106, 
108, I15, 129, 130 é¢ seg.; on 
gemmules, 60; on inheritance 
of acquired characters, 62, 69, 
107; and stability of the ma- 
terial basis of heredity, 63; on 
origin of sexual reproduction, 
103, 167. 

Gartner, on Malva, 80; on in- 
heritance of acquired characters 
in plants, 93. 

Gemmules, 2; Darwin on the 
size of, 4; and germ-plasm, 52, 
55, 58, 92, 105; and stirp, 58; 
Galton on, 60. 

Generative cells of the Hydro- 
medusae, Weismann on, 71, 109 5 
example of continuity of germ- 
plasm, 72-73. 

Germ-cells, and body-cells, 29, 
75-77; nucleo-plasm of, 30; 
number of 43, 45. 

Germ-plasm, Weismann’s theory 
of, 5, 105, 173 e¢ seg.; immor- 
tality of, 9, 24; continuity of, 9, 
18, 49, 56-67, 69-70, 72, 75, 


Lndex. 


78, 86-87, 104-105, I0g-IIO, 
114, 120, 168; differences in, 
12; origin of, 17; indepen- 
dence of, Ig; and natural selec- 
tion, 21; stability of, 22, 49, 
57, 66, 86-89, 91-93, 99-100, 
104-105, 109, I12-114, I51 
et seg.; lodged in nucleus, 29; 
and somato-plasm, 29, 81, 110; 
the modification of, 36; exami- 
nation of Weismann’s theory of, 
48 ; Weismann’s theory of and 
Pangenesis, 52; and gemmules, 
52, 55, §8, 105-106, 121; 
multiplication of in the general 
cellular tissues of plants, 53; 
De Vries on, 54; Differentiation 
of, 55; and ‘‘formative ma- 
terial,” 56; and stirp, 58-59, 
61, 75, 106; and somatic-idio- 
plasm, 69 ; as a basis of heredity, 
7°; ancestral germ-plasm, 123. 

Grafting, and the effect of the 
somatic-tissues on the germinal 
elements, 81-82; Darwin on, 
83; and bud-variation, 98; 
Weismann on, 126. 


H. 


Hackel, theory of heredity, 2. 

Hartog, Prof. M., on Weismann, 
155; on sexual propagation, 
166-167. 

Healing of wounds, 34. 

Henslow, Rev. G., on regenera- 
tion in plants, 53. 

Heredity, various theories of, 2, 
49, 70; statement of Weismann’s 
theory of, 17; modification of 
Weismann’s theory of, 28, 46, 
52, 65, 68, 75, 163 e¢ segs the 
nucleus and, 29; “carriers of,” 
22, 38, 70, 78,122 «) thearyyor 
and histology, 38; examination 
of Weismann’s theory of, 48, 
105, 117; comparison of Weis- 
mann’s, Darwin’s, and Galton’s 
theories of, 51, 105-106; criti- 
cism of Weismann’s theory of by 
Strasburger, 51; the material 
basis of, 61, 63. 


Index. 


Hertwig, O., theory of heredity, 2; 
on polar bodies, 46, 125. 

Hildebrand, or effect of pollen 
upon somatic tissues (Xenia), 
80; on Orchideae, 80. 

His, theory of heredity, 2. 

Hoffmann, on the _ inheritance 
of acquired characters, 93-4, 
II4. 

Hydromedusa:, Weismann on 
generative cells of, 71, 109; 
illustrate continuity of germ- 


plasm, 72-73. 


I 


Identical twins, 41. 

Idio-plasm, Nageli’s term, 31; A 
and Bb, 31-32; self-multiplica- 
tion of, 34; amount of idio- 
plasm A in the nucleus, 40. 

Lisi 2. 

Individual differences, Weismann, 
39, 41, 43. 

Influence of a previous sire upon 
the progeny of the same dam, 
see Telegony. 

Influence of external conditions, 
see Acquired characters. 

Influence of pollen upon somatic 
tissues, seé Xenia. 

Inheritance of acquired characters, 
see Acquired characters. 

Invertebrates, Weismann on sexual 
apparatus of, 72, 74, 109. 


Jelly-fish, regeneration in, 4. 
Jordan, on mheritance of acquired 
characters in plants, 93. 


K, 
Karyokinesis, 37. 


L. 


Lamarck, Weismann and, 16, 21. 
Lamarckian factors, importance 
of, 57, 59, 62, 65, 67, 69, 82, 
106 108, 111-112, 128, 147. 
Lile, duration of, 7, Io. 


219 


M. 


Malingié-Nouel, on Telegony, 
193 ef seq. 

Malva, Gartner on, 80. 

Maupas, on the Protozoa, 101, 
148. 

Metazoa and Metaphyta, cause of: 
mortality of, 7, 24, 148; rela- 
tion of progeny to parents in, 
16; transmission of acquired 
characters in, 16; propagaticn 
in, 51. 

Mivart, on inheritance of acquired 
characters, 94. 

Molecules, 54, 123. 

Morton, Earl of, on Telegony, 
192. 

Miller, Fritz, on bud-variation, 


Multicellular organisms, see Me- 
tazoa and Metaphyta. 


N. 


Nageli, theory of heredity, 2; and 
idio-plasm, 31, 187 ; and germ- 
plasm, 36; on inheritance of 
acquired characters in plants, 


Be 

NET selection, the cause of 
death, 8; action of, 20; the 
material for the operation of, 
13, 57; not the cause of sexual 
propagation, 13-14; and the 
Protozoa, 15, Iol-102; and 
germ-plasm, 21; sole cause of 
organic evolution, 25, 59, III, 
Lis 

Nouel, Malingié-, on Telegony, 
193 ef seq. 

Nucleo-plasm, of germ and soma- 
tic cells, 30. 

Nucleus, alone contains germ- 
plasm, 29; contains two 
substances, 33; and heredity, 
37; and polar bodies, 40; 
amount of idio-plasm A in, 40. 

Nutritive congenital changes, 64. 


2): 


Orchideae, Hildeband on, 80. 
Organic evolution, the cause of, 


220 


25; Weismann’s theory of, 26, 
48, 50, 58, 66, 68, 87, 100, 104, 
106-108, I14-115, 147. 

Ova, Weismann on the size of, 39. 


P. 


Pallas, on variability, 154. 

Pangenesis, Darwin’s theory of, 2, 
20; and Weismann’s theory of, 
52,55) 749 73) 12s ands Pan- 
mixia, 59-60 ; Galton on, 60. 

Panmixia, and Pangenesis, 59-50. 

Parthenogenetic organisms, and 
natural selection, 15; no con- 
genital variations in, 72, 75. 

Parthenogenetic ova, Weismann 
on, 45, 89, 91, 109. 

Phylogenesis, 34. 

Physiological isolation, of germ- 
cells, 74. 

Plants, reproductive cells of, 74; 
influence of pollen upon so- 
matic tissues of (Xenia), 78-80; 
bud-variation in, 9%, 94-99; 
Hoffmann’s investigations on 
the inheritance of acquired char- 
acters in, 93. 

Polar bodies, Weismann on, 40, 
46, 125; examination of Weis- 
mann’s explanation of, 42; 
O. Hertwig on, 46, 125. 

Protophyta, natural selection and, 
114. 

Protozoa, immortality of, 7; and 
natural selection, 15, 114; 
origin of species of, 15, 102; 
action of environment on, 15; 
Maupas on, Iol. 


AS. 


Regeneration, in sea-anemones and 
jelly-fish, 4, 353; of ‘an entire 
organism, 34; Weismann on, 
51 et seg.; in Begonia, 52; 
Rev. G. Henslow on, 53; and 
stirp, 59. 

Rejuvenescence, 166. 

Representative congenital changes, 
65. 

Reproduction, essential meaning 


L[ndex. 


of sexual, 8, 11; in the Pro- 
tozoa, 16; somatic. 35. 

Reproductive elements, potential 
immortality of,g ; of Vertebrates 
and Plants, 74. 

Reversion, 3, 91, 105. 

Roux, on the principle of “ strug- 
gle,” 1309. 


S. 


Sea-anemones, regeneration in, 4. 

Sexual apparatus of Invertebrates, 
Weismann on, 72,.74. 

Sexual-cells and somatic-cells, 75 - 
77, 81, 84. 

Sexual propagation, — essential 
meaning of, 8, 11, 87; sole 
cause of congenital variations, 
12, 89-90, 102, 135, T41, 153, 
158; did not arise through the 
agency of natural selection, 13— 
14; in multicellular organisms, 
51; Galton on the origin of, 
1033; in Cytisus adamt?, 127. 

Significance of sexual reproduction, 
see Sexual Reproduction. 

Somatic-cells, nucleo-plasm of, 30; 
and sexual-cells, 75-77, 81, 84. 

Somatic-idio-plasm, 32-33; and 
germ-plasm, 69. 

Somatic reproduction, 35, 52. 

Somato-plasm and germ-plasm, 
29. 

EB eeiniied congenital changes, 65. 

Species, Weismann on the origin of 
new, 100-101. 

Spencer, Herbert, theory of 
heredity, 2; on Telegony, 191 
et Seq. ; 

Stability of germ-plasm, see Germ- 
plasm. 

Stirp, and gemmules, 58-59, 61; 
and somatic tissues,60; and the 
germinal cells of Hydromedusae, 
73; and germ-plasm, 75, 92, 
106, 133. 

Strasburger, on Weismann’s 
theory of heredity, 51; on the 
origin of sexual propagation, 
andr yg 

Stylenichia, Maupas on, Iol. 

Summary, 103. 


Lndex. 


iy 


Telegony, 77-79, 110, 141 ef seq., 
Igi et seq. 

Transmission of acquired char- 
acters, see Acquired characters. 

Twins, identical, 41. 


U. 


Unicellular organisms, reproduc- 
tion of, 16; action of environ- 
ment on, 23, 147 e¢ seg.; poten- 
tially immortal, 23; natural 
selection and the, 24, 57, 114; 
and the origin of hereditary in- 
dividual variations, 100. 


We 


Variation, see Congenital varia- 
tions, Acquired characters, &c.; 
Darwin on the causes of, 102; 
Weismann on the origin of, 
153. 

Veitebrates, reproductive cells of, 
74- 

Vestigial organs, persistence of, 
gl. 

Vines, Prof. S., criticism on 
Weismann, 14, 75, 90, 99, 152, 
178; on the Basidiomycetes, go. 

’ Vries, De, theory of heredity, 2 

on germ-plasm, 54; on the 

chromatophores of Algae, 83, 

III; on Xenia, 144. 


W. 


Weismann, Prof. August., 
theory of germ-plasm, 5, 17, 
173 e¢ seg.; on the duration of 
life, 7, 10; onthe essential meaning 
of sexual propagation, 11, 103, 
135, 141; on natural selection 
as the origin of sexual repro- 
duction, 14; on Prof. Vines’ 
criticism, 14, 90, 99, 178 ef seq. ; 
on the Protozoa and natural se- 
lection, 15, 102; on Lamarck, 
10; on adaptive development, 
Ig; and natural selection, 21; 
summary of theory of germ- 
plasm, 23; theory of organic 


Pe | 


evolution, 26, 48, 50, 58, 66, 68, 
87, 100, 104, 106-108, 114-115, 
147; modifications of theory of 
heredity, 28, 46, 52, 65, 68, 75, 
163 ef seg.; and of selimuls 
tiplication of idio- plasm, 34; 
on ‘‘ontogenetic grades,” 35, 
53; on the modification of germ- 
plasm, 36; on chromatin, 38 ; 

on individual differences, 39, 
41, 43; on the size of ova, 
39; on polar bodies, 40, 42, 46, 
125; on the number of germ- 
cells, 44-45 ; on parthenogenetic 
ova, 45, 89, 91; examination 
of his theory of germ-plasm or 
heredity, 48, 85; on the stability 
and continuity of germ-plasm, 
49, 63, 66, 86-89, 91-93, 99- 
100, 103-105, 107, 109-110, 
112-114, 120, 151, 158; com- 
parison of his theory with those 
of Darwin and Galton, 41, 58; 
on Strasburger’s criticism of his 
theory, 52 ; on the multiplication 
of germ-plasm in the general 
cellular tissues of plants, 53; 
on regeneration in plants, 53; 
anticipated by Galton, 59, 68; 
and Galton, 63, 130 e¢ seq.; 
on transmission of acquired 
characters, 67, 83, 96, III, 
127; and his critics, 70; on the 
Hydromedusae, 71, 109; on the 
sexualapparatus of Invertebrates, 
72; and the influence of germ- 
cells upon somatic tissues (‘Tele- 
gony and Xenia), 80-81, 196 


et seg.; and the significance 
of grafting, 81-82, 126; and 
vestigial characters, 92; on 


Hoffmann’s investigations, 93 ; 

on bud-variation, 95, 97, 161; 

on the origin of hereditary 

individual variations, 100-101 ; 

on the origin of new species, 1o1. 
Wounds, healing of, 34. 


X. 
Xenia, 78-81, 110, 141, 144 e¢ seg. 


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